From: Thierry Reding treding@nvidia.com
Hi,
this is an alternative proposal to fix panel support on Venice 2 and Nyan. Dmitry had proposed a different solution that involved reverting the I2C/DDC registration order and would complicate things by breaking the encapsulation of the driver by introducing a global (though locally scoped) variable[0].
This set of patches avoids that by using the recently introduced DP AUX bus infrastructure. The result is that the changes are actually less intrusive and not a step back. Instead they nicely remove the circular dependency that previously existed and caused these issues in the first place.
To be fair, this is not perfect either because it requires a device tree change and hence isn't technically backwards-compatible. However, given that the original device tree was badly broken in the first place, I think we can make an exception, especially since it is not generally a problem to update device trees on the affected devices.
Secondly, this relies on infrastructure that was introduced in v5.15 and therefore will be difficult to backport beyond that. However, since this functionality has been broken since v5.13 and all of the kernel versions between that and v5.15 are EOL anyway, there isn't much that we can do to fix the interim versions anyway.
Adding Doug and Laurent since they originally designed the AUX bus patches in case they see anything in here that would be objectionable.
Thierry
[0]: https://lore.kernel.org/dri-devel/20211130230957.30213-1-digetx@gmail.com/
Thierry Reding (2): drm/tegra: dpaux: Populate AUX bus ARM: tegra: Move panels to AUX bus
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 5 files changed, 33 insertions(+), 19 deletions(-)
From: Thierry Reding treding@nvidia.com
The DPAUX hardware block exposes an DP AUX interface that provides access to an AUX bus and the devices on that bus. Use the DP AUX bus infrastructure that was recently introduced to probe devices on this bus from DT.
Signed-off-by: Thierry Reding treding@nvidia.com --- drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 2 files changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/tegra/Kconfig b/drivers/gpu/drm/tegra/Kconfig index 8cf5aeb9db6c..201f5175ecfe 100644 --- a/drivers/gpu/drm/tegra/Kconfig +++ b/drivers/gpu/drm/tegra/Kconfig @@ -5,6 +5,7 @@ config DRM_TEGRA depends on COMMON_CLK depends on DRM depends on OF + select DRM_DP_AUX_BUS select DRM_KMS_HELPER select DRM_MIPI_DSI select DRM_PANEL diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c index 1f96e416fa08..9da1edcdc835 100644 --- a/drivers/gpu/drm/tegra/dpaux.c +++ b/drivers/gpu/drm/tegra/dpaux.c @@ -18,6 +18,7 @@ #include <linux/reset.h> #include <linux/workqueue.h>
+#include <drm/drm_dp_aux_bus.h> #include <drm/drm_dp_helper.h> #include <drm/drm_panel.h>
@@ -570,6 +571,12 @@ static int tegra_dpaux_probe(struct platform_device *pdev) list_add_tail(&dpaux->list, &dpaux_list); mutex_unlock(&dpaux_lock);
+ err = devm_of_dp_aux_populate_ep_devices(&dpaux->aux); + if (err < 0) { + dev_err(dpaux->dev, "failed to populate AUX bus: %d\n", err); + return err; + } + return 0; }
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
The DPAUX hardware block exposes an DP AUX interface that provides access to an AUX bus and the devices on that bus. Use the DP AUX bus infrastructure that was recently introduced to probe devices on this bus from DT.
Signed-off-by: Thierry Reding treding@nvidia.com
drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 2 files changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/tegra/Kconfig b/drivers/gpu/drm/tegra/Kconfig index 8cf5aeb9db6c..201f5175ecfe 100644 --- a/drivers/gpu/drm/tegra/Kconfig +++ b/drivers/gpu/drm/tegra/Kconfig @@ -5,6 +5,7 @@ config DRM_TEGRA depends on COMMON_CLK depends on DRM depends on OF
- select DRM_DP_AUX_BUS select DRM_KMS_HELPER select DRM_MIPI_DSI select DRM_PANEL
diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c index 1f96e416fa08..9da1edcdc835 100644 --- a/drivers/gpu/drm/tegra/dpaux.c +++ b/drivers/gpu/drm/tegra/dpaux.c @@ -18,6 +18,7 @@ #include <linux/reset.h> #include <linux/workqueue.h>
+#include <drm/drm_dp_aux_bus.h> #include <drm/drm_dp_helper.h> #include <drm/drm_panel.h>
@@ -570,6 +571,12 @@ static int tegra_dpaux_probe(struct platform_device *pdev) list_add_tail(&dpaux->list, &dpaux_list); mutex_unlock(&dpaux_lock);
- err = devm_of_dp_aux_populate_ep_devices(&dpaux->aux);
- if (err < 0) {
dev_err(dpaux->dev, "failed to populate AUX bus: %d\n", err);return err;- }
- return 0;
}
Needs stable tag for 5.15+.
Hi,
On Mon, Dec 20, 2021 at 2:49 AM Thierry Reding thierry.reding@gmail.com wrote:
From: Thierry Reding treding@nvidia.com
The DPAUX hardware block exposes an DP AUX interface that provides access to an AUX bus and the devices on that bus. Use the DP AUX bus infrastructure that was recently introduced to probe devices on this bus from DT.
Signed-off-by: Thierry Reding treding@nvidia.com
drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 2 files changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/tegra/Kconfig b/drivers/gpu/drm/tegra/Kconfig index 8cf5aeb9db6c..201f5175ecfe 100644 --- a/drivers/gpu/drm/tegra/Kconfig +++ b/drivers/gpu/drm/tegra/Kconfig @@ -5,6 +5,7 @@ config DRM_TEGRA depends on COMMON_CLK depends on DRM depends on OF
select DRM_DP_AUX_BUS select DRM_KMS_HELPER select DRM_MIPI_DSI select DRM_PANELdiff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c index 1f96e416fa08..9da1edcdc835 100644 --- a/drivers/gpu/drm/tegra/dpaux.c +++ b/drivers/gpu/drm/tegra/dpaux.c @@ -18,6 +18,7 @@ #include <linux/reset.h> #include <linux/workqueue.h>
+#include <drm/drm_dp_aux_bus.h> #include <drm/drm_dp_helper.h> #include <drm/drm_panel.h>
@@ -570,6 +571,12 @@ static int tegra_dpaux_probe(struct platform_device *pdev) list_add_tail(&dpaux->list, &dpaux_list); mutex_unlock(&dpaux_lock);
err = devm_of_dp_aux_populate_ep_devices(&dpaux->aux);if (err < 0) {dev_err(dpaux->dev, "failed to populate AUX bus: %d\n", err);return err;
nit:
if (err < 0) return dev_err_probe(dpaux->dev, err, "failed to populate AUX bus\n");
That's more concise and gives the pretty formatting for the error code (not that devm_of_dp_aux_populate_ep_devices() currently returns anything other than 0).
}
I think you need to use of_dp_aux_populate_ep_devices() and then depopulate in your remove, right? Otherwise the ordering won't be right. Either that or fully transition your probe to devm (and get rid of your remove) by adding some devm_add_action_or_reset() helpers...
Hrm, I guess looking closer it's also a little concerning that if devm_of_dp_aux_populate_ep_devices() returns an error then you'll totally skip all the things that tegra_dpaux_remove() is supposed to handle. I guess that's a pre-existing bug (earlier error cases in the probe don't, for instance, undo the pm_runtime state) but this makes it worse.
-Doug
From: Thierry Reding treding@nvidia.com
Move the eDP panel on Venice 2 and Nyan boards into the corresponding AUX bus device tree node. This allows us to avoid a nasty circular dependency that would otherwise be created between the DPAUX and panel nodes via the DDC/I2C phandle.
Signed-off-by: Thierry Reding treding@nvidia.com --- arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- 3 files changed, 25 insertions(+), 19 deletions(-)
diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts b/arch/arm/boot/dts/tegra124-nyan-big.dts index 1d2aac2cb6d0..fdc1d64dfff9 100644 --- a/arch/arm/boot/dts/tegra124-nyan-big.dts +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts @@ -13,12 +13,15 @@ / { "google,nyan-big-rev1", "google,nyan-big-rev0", "google,nyan-big", "google,nyan", "nvidia,tegra124";
- panel: panel { - compatible = "auo,b133xtn01"; - - power-supply = <&vdd_3v3_panel>; - backlight = <&backlight>; - ddc-i2c-bus = <&dpaux>; + host1x@50000000 { + dpaux@545c0000 { + aux-bus { + panel: panel { + compatible = "auo,b133xtn01"; + backlight = <&backlight>; + }; + }; + }; };
mmc@700b0400 { /* SD Card on this bus */ diff --git a/arch/arm/boot/dts/tegra124-nyan-blaze.dts b/arch/arm/boot/dts/tegra124-nyan-blaze.dts index 677babde6460..abdf4456826f 100644 --- a/arch/arm/boot/dts/tegra124-nyan-blaze.dts +++ b/arch/arm/boot/dts/tegra124-nyan-blaze.dts @@ -15,12 +15,15 @@ / { "google,nyan-blaze-rev0", "google,nyan-blaze", "google,nyan", "nvidia,tegra124";
- panel: panel { - compatible = "samsung,ltn140at29-301"; - - power-supply = <&vdd_3v3_panel>; - backlight = <&backlight>; - ddc-i2c-bus = <&dpaux>; + host1x@50000000 { + dpaux@545c0000 { + aux-bus { + panel: panel { + compatible = "samsung,ltn140at29-301"; + backlight = <&backlight>; + }; + }; + }; };
sound { diff --git a/arch/arm/boot/dts/tegra124-venice2.dts b/arch/arm/boot/dts/tegra124-venice2.dts index 232c90604df9..6a9592ceb5f2 100644 --- a/arch/arm/boot/dts/tegra124-venice2.dts +++ b/arch/arm/boot/dts/tegra124-venice2.dts @@ -48,6 +48,13 @@ sor@54540000 { dpaux@545c0000 { vdd-supply = <&vdd_3v3_panel>; status = "okay"; + + aux-bus { + panel: panel { + compatible = "lg,lp129qe"; + backlight = <&backlight>; + }; + }; }; };
@@ -1080,13 +1087,6 @@ power { }; };
- panel: panel { - compatible = "lg,lp129qe"; - power-supply = <&vdd_3v3_panel>; - backlight = <&backlight>; - ddc-i2c-bus = <&dpaux>; - }; - vdd_mux: regulator-mux { compatible = "regulator-fixed"; regulator-name = "+VDD_MUX";
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Move the eDP panel on Venice 2 and Nyan boards into the corresponding AUX bus device tree node. This allows us to avoid a nasty circular dependency that would otherwise be created between the DPAUX and panel nodes via the DDC/I2C phandle.
Signed-off-by: Thierry Reding treding@nvidia.com
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- 3 files changed, 25 insertions(+), 19 deletions(-)
diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts b/arch/arm/boot/dts/tegra124-nyan-big.dts index 1d2aac2cb6d0..fdc1d64dfff9 100644 --- a/arch/arm/boot/dts/tegra124-nyan-big.dts +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts @@ -13,12 +13,15 @@ / { "google,nyan-big-rev1", "google,nyan-big-rev0", "google,nyan-big", "google,nyan", "nvidia,tegra124";
- panel: panel {
compatible = "auo,b133xtn01";power-supply = <&vdd_3v3_panel>;backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;
host1x@50000000 {
dpaux@545c0000 {aux-bus {panel: panel {compatible = "auo,b133xtn01";backlight = <&backlight>;};};};};
mmc@700b0400 { /* SD Card on this bus */
diff --git a/arch/arm/boot/dts/tegra124-nyan-blaze.dts b/arch/arm/boot/dts/tegra124-nyan-blaze.dts index 677babde6460..abdf4456826f 100644 --- a/arch/arm/boot/dts/tegra124-nyan-blaze.dts +++ b/arch/arm/boot/dts/tegra124-nyan-blaze.dts @@ -15,12 +15,15 @@ / { "google,nyan-blaze-rev0", "google,nyan-blaze", "google,nyan", "nvidia,tegra124";
- panel: panel {
compatible = "samsung,ltn140at29-301";power-supply = <&vdd_3v3_panel>;backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;
host1x@50000000 {
dpaux@545c0000 {aux-bus {panel: panel {compatible = "samsung,ltn140at29-301";backlight = <&backlight>;};};};};
sound {
diff --git a/arch/arm/boot/dts/tegra124-venice2.dts b/arch/arm/boot/dts/tegra124-venice2.dts index 232c90604df9..6a9592ceb5f2 100644 --- a/arch/arm/boot/dts/tegra124-venice2.dts +++ b/arch/arm/boot/dts/tegra124-venice2.dts @@ -48,6 +48,13 @@ sor@54540000 { dpaux@545c0000 { vdd-supply = <&vdd_3v3_panel>; status = "okay";
aux-bus {panel: panel {compatible = "lg,lp129qe";backlight = <&backlight>;};};@@ -1080,13 +1087,6 @@ power { }; };
- panel: panel {
compatible = "lg,lp129qe";power-supply = <&vdd_3v3_panel>;backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;- };
- vdd_mux: regulator-mux { compatible = "regulator-fixed"; regulator-name = "+VDD_MUX";
You should add stable tag for 5.15 and also add separate patch to update the new arch/arm/boot/dts/tegra124-nyan-big-fhd.dts which we have in -next now.
22.12.2021 22:30, Dmitry Osipenko пишет:
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Move the eDP panel on Venice 2 and Nyan boards into the corresponding AUX bus device tree node. This allows us to avoid a nasty circular dependency that would otherwise be created between the DPAUX and panel nodes via the DDC/I2C phandle.
Signed-off-by: Thierry Reding treding@nvidia.com
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- 3 files changed, 25 insertions(+), 19 deletions(-)
diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts b/arch/arm/boot/dts/tegra124-nyan-big.dts index 1d2aac2cb6d0..fdc1d64dfff9 100644 --- a/arch/arm/boot/dts/tegra124-nyan-big.dts +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts @@ -13,12 +13,15 @@ / { "google,nyan-big-rev1", "google,nyan-big-rev0", "google,nyan-big", "google,nyan", "nvidia,tegra124";
- panel: panel {
compatible = "auo,b133xtn01";power-supply = <&vdd_3v3_panel>;backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;
host1x@50000000 {
dpaux@545c0000 {aux-bus {panel: panel {compatible = "auo,b133xtn01";backlight = <&backlight>;};};};};
mmc@700b0400 { /* SD Card on this bus */
diff --git a/arch/arm/boot/dts/tegra124-nyan-blaze.dts b/arch/arm/boot/dts/tegra124-nyan-blaze.dts index 677babde6460..abdf4456826f 100644 --- a/arch/arm/boot/dts/tegra124-nyan-blaze.dts +++ b/arch/arm/boot/dts/tegra124-nyan-blaze.dts @@ -15,12 +15,15 @@ / { "google,nyan-blaze-rev0", "google,nyan-blaze", "google,nyan", "nvidia,tegra124";
- panel: panel {
compatible = "samsung,ltn140at29-301";power-supply = <&vdd_3v3_panel>;backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;
host1x@50000000 {
dpaux@545c0000 {aux-bus {panel: panel {compatible = "samsung,ltn140at29-301";backlight = <&backlight>;};};};};
sound {
diff --git a/arch/arm/boot/dts/tegra124-venice2.dts b/arch/arm/boot/dts/tegra124-venice2.dts index 232c90604df9..6a9592ceb5f2 100644 --- a/arch/arm/boot/dts/tegra124-venice2.dts +++ b/arch/arm/boot/dts/tegra124-venice2.dts @@ -48,6 +48,13 @@ sor@54540000 { dpaux@545c0000 { vdd-supply = <&vdd_3v3_panel>; status = "okay";
aux-bus {panel: panel {compatible = "lg,lp129qe";backlight = <&backlight>;};};@@ -1080,13 +1087,6 @@ power { }; };
- panel: panel {
compatible = "lg,lp129qe";power-supply = <&vdd_3v3_panel>;backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;- };
- vdd_mux: regulator-mux { compatible = "regulator-fixed"; regulator-name = "+VDD_MUX";
You should add stable tag for 5.15 and also add separate patch to update the new arch/arm/boot/dts/tegra124-nyan-big-fhd.dts which we have in -next now.
Thierry, are you going to address this review comment? I see in linux-next that you picked up this incomplete version of the patch.
On Sun, Mar 06, 2022 at 08:59:13PM +0300, Dmitry Osipenko wrote:
22.12.2021 22:30, Dmitry Osipenko пишет:
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Move the eDP panel on Venice 2 and Nyan boards into the corresponding AUX bus device tree node. This allows us to avoid a nasty circular dependency that would otherwise be created between the DPAUX and panel nodes via the DDC/I2C phandle.
Signed-off-by: Thierry Reding treding@nvidia.com
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- 3 files changed, 25 insertions(+), 19 deletions(-)
diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts b/arch/arm/boot/dts/tegra124-nyan-big.dts index 1d2aac2cb6d0..fdc1d64dfff9 100644 --- a/arch/arm/boot/dts/tegra124-nyan-big.dts +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts @@ -13,12 +13,15 @@ / { "google,nyan-big-rev1", "google,nyan-big-rev0", "google,nyan-big", "google,nyan", "nvidia,tegra124";
- panel: panel {
compatible = "auo,b133xtn01";power-supply = <&vdd_3v3_panel>;backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;
host1x@50000000 {
dpaux@545c0000 {aux-bus {panel: panel {compatible = "auo,b133xtn01";backlight = <&backlight>;};};};};
mmc@700b0400 { /* SD Card on this bus */
diff --git a/arch/arm/boot/dts/tegra124-nyan-blaze.dts b/arch/arm/boot/dts/tegra124-nyan-blaze.dts index 677babde6460..abdf4456826f 100644 --- a/arch/arm/boot/dts/tegra124-nyan-blaze.dts +++ b/arch/arm/boot/dts/tegra124-nyan-blaze.dts @@ -15,12 +15,15 @@ / { "google,nyan-blaze-rev0", "google,nyan-blaze", "google,nyan", "nvidia,tegra124";
- panel: panel {
compatible = "samsung,ltn140at29-301";power-supply = <&vdd_3v3_panel>;backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;
host1x@50000000 {
dpaux@545c0000 {aux-bus {panel: panel {compatible = "samsung,ltn140at29-301";backlight = <&backlight>;};};};};
sound {
diff --git a/arch/arm/boot/dts/tegra124-venice2.dts b/arch/arm/boot/dts/tegra124-venice2.dts index 232c90604df9..6a9592ceb5f2 100644 --- a/arch/arm/boot/dts/tegra124-venice2.dts +++ b/arch/arm/boot/dts/tegra124-venice2.dts @@ -48,6 +48,13 @@ sor@54540000 { dpaux@545c0000 { vdd-supply = <&vdd_3v3_panel>; status = "okay";
aux-bus {panel: panel {compatible = "lg,lp129qe";backlight = <&backlight>;};};@@ -1080,13 +1087,6 @@ power { }; };
- panel: panel {
compatible = "lg,lp129qe";power-supply = <&vdd_3v3_panel>;backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;- };
- vdd_mux: regulator-mux { compatible = "regulator-fixed"; regulator-name = "+VDD_MUX";
You should add stable tag for 5.15 and also add separate patch to update the new arch/arm/boot/dts/tegra124-nyan-big-fhd.dts which we have in -next now.
Thierry, are you going to address this review comment? I see in linux-next that you picked up this incomplete version of the patch.
Ah, shoot. I've got this in my local tree but forgot to squash this in with the other changes. I'll send out a follow-up.
Thierry
Hi,
On Mon, Dec 20, 2021 at 2:49 AM Thierry Reding thierry.reding@gmail.com wrote:
From: Thierry Reding treding@nvidia.com
Move the eDP panel on Venice 2 and Nyan boards into the corresponding AUX bus device tree node. This allows us to avoid a nasty circular dependency that would otherwise be created between the DPAUX and panel nodes via the DDC/I2C phandle.
Signed-off-by: Thierry Reding treding@nvidia.com
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- 3 files changed, 25 insertions(+), 19 deletions(-)
diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts b/arch/arm/boot/dts/tegra124-nyan-big.dts index 1d2aac2cb6d0..fdc1d64dfff9 100644 --- a/arch/arm/boot/dts/tegra124-nyan-big.dts +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts @@ -13,12 +13,15 @@ / { "google,nyan-big-rev1", "google,nyan-big-rev0", "google,nyan-big", "google,nyan", "nvidia,tegra124";
panel: panel {compatible = "auo,b133xtn01";power-supply = <&vdd_3v3_panel>;
You remove the "power-supply" line here but don't add it below. Isn't that a problem? power-supply for the panel is listed as "required" in the panel dt bindings so I presume this will increase validation warnings?
backlight = <&backlight>;ddc-i2c-bus = <&dpaux>;
host1x@50000000 {dpaux@545c0000 {
Optional nit: on other SoC dts files I've always had the policy to try to avoid replicating hierarchies like this (host1x@50000000 => dpaux@545c0000). Instead I'd express this as:
&dpaux { aux-bux { panel: panel { ... }; }; };
aux-bus {panel: panel {compatible = "auo,b133xtn01";backlight = <&backlight>;
nit: In theory the "backlight" could go in tegra124-nyan.dtsi, right? Then you just need to override the compatible...
-Doug
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Hi,
this is an alternative proposal to fix panel support on Venice 2 and Nyan. Dmitry had proposed a different solution that involved reverting the I2C/DDC registration order and would complicate things by breaking the encapsulation of the driver by introducing a global (though locally scoped) variable[0].
This set of patches avoids that by using the recently introduced DP AUX bus infrastructure. The result is that the changes are actually less intrusive and not a step back. Instead they nicely remove the circular dependency that previously existed and caused these issues in the first place.
To be fair, this is not perfect either because it requires a device tree change and hence isn't technically backwards-compatible. However, given that the original device tree was badly broken in the first place, I think we can make an exception, especially since it is not generally a problem to update device trees on the affected devices.
Secondly, this relies on infrastructure that was introduced in v5.15 and therefore will be difficult to backport beyond that. However, since this functionality has been broken since v5.13 and all of the kernel versions between that and v5.15 are EOL anyway, there isn't much that we can do to fix the interim versions anyway.
Adding Doug and Laurent since they originally designed the AUX bus patches in case they see anything in here that would be objectionable.
Thierry
Thierry Reding (2): drm/tegra: dpaux: Populate AUX bus ARM: tegra: Move panels to AUX bus
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 5 files changed, 33 insertions(+), 19 deletions(-)
It should "work" since you removed the ddc-i2c-bus phandle from the panel nodes, and thus, panel->ddc won't be used during panel-edp driver probe. But this looks like a hack rather than a fix.
I'm not sure why and how devm_of_dp_aux_populate_ep_devices() usage should be relevant here. The drm_dp_aux_register() still should to invoked before devm_of_dp_aux_populate_ep_devices(), otherwise panel->ddc adapter won't be registered.
The panel->ddc isn't used by the new panel-edp driver unless panel is compatible with "edp-panel". Hence the generic_edp_panel_probe() should either fail or crash for a such "edp-panel" since panel->ddc isn't fully instantiated, AFAICS.
On Mon, Dec 20, 2021 at 05:45:41PM +0300, Dmitry Osipenko wrote:
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Hi,
this is an alternative proposal to fix panel support on Venice 2 and Nyan. Dmitry had proposed a different solution that involved reverting the I2C/DDC registration order and would complicate things by breaking the encapsulation of the driver by introducing a global (though locally scoped) variable[0].
This set of patches avoids that by using the recently introduced DP AUX bus infrastructure. The result is that the changes are actually less intrusive and not a step back. Instead they nicely remove the circular dependency that previously existed and caused these issues in the first place.
To be fair, this is not perfect either because it requires a device tree change and hence isn't technically backwards-compatible. However, given that the original device tree was badly broken in the first place, I think we can make an exception, especially since it is not generally a problem to update device trees on the affected devices.
Secondly, this relies on infrastructure that was introduced in v5.15 and therefore will be difficult to backport beyond that. However, since this functionality has been broken since v5.13 and all of the kernel versions between that and v5.15 are EOL anyway, there isn't much that we can do to fix the interim versions anyway.
Adding Doug and Laurent since they originally designed the AUX bus patches in case they see anything in here that would be objectionable.
Thierry
Thierry Reding (2): drm/tegra: dpaux: Populate AUX bus ARM: tegra: Move panels to AUX bus
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 5 files changed, 33 insertions(+), 19 deletions(-)
It should "work" since you removed the ddc-i2c-bus phandle from the panel nodes, and thus, panel->ddc won't be used during panel-edp driver probe. But this looks like a hack rather than a fix.
The AUX ->ddc will be used for panel->ddc if the ddc-i2c-bus property is not specified. And that makes perfect sense because we'd basically just be pointing back to the AUX node anyway.
I'm not sure why and how devm_of_dp_aux_populate_ep_devices() usage should be relevant here. The drm_dp_aux_register() still should to invoked before devm_of_dp_aux_populate_ep_devices(), otherwise panel->ddc adapter won't be registered.
drm_dp_aux_register() is only needed to expose the device to userspace and make the I2C adapter available to the rest of the system. But since we already know the AUX and I2C adapter, we can use it directly without doing a separate lookup. drm_dp_aux_init() should be enough to set the adapter up to work for what we need.
See also the kerneldoc for drm_dp_aux_register() where this is described in a bit more detail.
The panel->ddc isn't used by the new panel-edp driver unless panel is compatible with "edp-panel". Hence the generic_edp_panel_probe() should either fail or crash for a such "edp-panel" since panel->ddc isn't fully instantiated, AFAICS.
I've tested this and it works fine on Venice 2. Since that was the reference design for Nyan, I suspect that Nyan's will also work.
It'd be great if Thomas or anyone else with access to a Nyan could test this to verify that.
Thierry
20.12.2021 18:27, Thierry Reding пишет:
On Mon, Dec 20, 2021 at 05:45:41PM +0300, Dmitry Osipenko wrote:
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Hi,
this is an alternative proposal to fix panel support on Venice 2 and Nyan. Dmitry had proposed a different solution that involved reverting the I2C/DDC registration order and would complicate things by breaking the encapsulation of the driver by introducing a global (though locally scoped) variable[0].
This set of patches avoids that by using the recently introduced DP AUX bus infrastructure. The result is that the changes are actually less intrusive and not a step back. Instead they nicely remove the circular dependency that previously existed and caused these issues in the first place.
To be fair, this is not perfect either because it requires a device tree change and hence isn't technically backwards-compatible. However, given that the original device tree was badly broken in the first place, I think we can make an exception, especially since it is not generally a problem to update device trees on the affected devices.
Secondly, this relies on infrastructure that was introduced in v5.15 and therefore will be difficult to backport beyond that. However, since this functionality has been broken since v5.13 and all of the kernel versions between that and v5.15 are EOL anyway, there isn't much that we can do to fix the interim versions anyway.
Adding Doug and Laurent since they originally designed the AUX bus patches in case they see anything in here that would be objectionable.
Thierry
Thierry Reding (2): drm/tegra: dpaux: Populate AUX bus ARM: tegra: Move panels to AUX bus
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 5 files changed, 33 insertions(+), 19 deletions(-)
It should "work" since you removed the ddc-i2c-bus phandle from the panel nodes, and thus, panel->ddc won't be used during panel-edp driver probe. But this looks like a hack rather than a fix.
The AUX ->ddc will be used for panel->ddc if the ddc-i2c-bus property is not specified. And that makes perfect sense because we'd basically just be pointing back to the AUX node anyway.
I'm not sure why and how devm_of_dp_aux_populate_ep_devices() usage should be relevant here. The drm_dp_aux_register() still should to invoked before devm_of_dp_aux_populate_ep_devices(), otherwise panel->ddc adapter won't be registered.
drm_dp_aux_register() is only needed to expose the device to userspace and make the I2C adapter available to the rest of the system. But since we already know the AUX and I2C adapter, we can use it directly without doing a separate lookup. drm_dp_aux_init() should be enough to set the adapter up to work for what we need.
See also the kerneldoc for drm_dp_aux_register() where this is described in a bit more detail.
Alright, so you fixed it by removing the ddc-i2c-bus phandles and I2C DDC will work properly anyways with that on v5.16.
But the aux-bus usage still is irrelevant for the fix. Let's not use it then.
The panel->ddc isn't used by the new panel-edp driver unless panel is compatible with "edp-panel". Hence the generic_edp_panel_probe() should either fail or crash for a such "edp-panel" since panel->ddc isn't fully instantiated, AFAICS.
I've tested this and it works fine on Venice 2. Since that was the reference design for Nyan, I suspect that Nyan's will also work.
It'd be great if Thomas or anyone else with access to a Nyan could test this to verify that.
There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, 2023, hence we need to either use:
Approach #1:
1. apply my variant of the fix 2. backport it to v5.15 3. apply your variant without aux-bus, replacing my fix on 5.16+
Or
Approach #2:
1. remove ddc-i2c-bus phandles in DTs 2. backport (?) it to v5.15 3. apply your variant without aux-bus
Or
Approach #3:
1. ignore v5.15 and keep it screwed 2. apply your variant as is
Which approach will you prefer?
I'm not happy that older DTBs will be broken. Can we do better about it?
Is it possible to patch DT in the code by removing the ddc-i2c-bus phandle?
Or can we patch panel-simple on 5.15 and panel-edp on 5.16, making these drivers to skip ddc-i2c-bus on Tegra+eDP? The eDP driver fixup will be trivial, fixing older panel-simple will be more invasive.
I think the best solution will be to use Approach #1 and in the end complete it with this panel-edp workaround below. This approach will have minimal code impact on 5.16+ kernels and will keep older DTBs working. Are you okay with this?
diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c index 176ef0c3cc1d..4e5b84324659 100644 --- a/drivers/gpu/drm/panel/panel-edp.c +++ b/drivers/gpu/drm/panel/panel-edp.c @@ -793,7 +793,11 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc, return err; }
- ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0); + if (of_machine_is_compatible("nvidia,tegra124")) + ddc = NULL; + else + ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0); + if (ddc) { panel->ddc = of_find_i2c_adapter_by_node(ddc); of_node_put(ddc);
20.12.2021 19:12, Dmitry Osipenko пишет:
20.12.2021 18:27, Thierry Reding пишет:
On Mon, Dec 20, 2021 at 05:45:41PM +0300, Dmitry Osipenko wrote:
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Hi,
this is an alternative proposal to fix panel support on Venice 2 and Nyan. Dmitry had proposed a different solution that involved reverting the I2C/DDC registration order and would complicate things by breaking the encapsulation of the driver by introducing a global (though locally scoped) variable[0].
This set of patches avoids that by using the recently introduced DP AUX bus infrastructure. The result is that the changes are actually less intrusive and not a step back. Instead they nicely remove the circular dependency that previously existed and caused these issues in the first place.
To be fair, this is not perfect either because it requires a device tree change and hence isn't technically backwards-compatible. However, given that the original device tree was badly broken in the first place, I think we can make an exception, especially since it is not generally a problem to update device trees on the affected devices.
Secondly, this relies on infrastructure that was introduced in v5.15 and therefore will be difficult to backport beyond that. However, since this functionality has been broken since v5.13 and all of the kernel versions between that and v5.15 are EOL anyway, there isn't much that we can do to fix the interim versions anyway.
Adding Doug and Laurent since they originally designed the AUX bus patches in case they see anything in here that would be objectionable.
Thierry
Thierry Reding (2): drm/tegra: dpaux: Populate AUX bus ARM: tegra: Move panels to AUX bus
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 5 files changed, 33 insertions(+), 19 deletions(-)
It should "work" since you removed the ddc-i2c-bus phandle from the panel nodes, and thus, panel->ddc won't be used during panel-edp driver probe. But this looks like a hack rather than a fix.
The AUX ->ddc will be used for panel->ddc if the ddc-i2c-bus property is not specified. And that makes perfect sense because we'd basically just be pointing back to the AUX node anyway.
I'm not sure why and how devm_of_dp_aux_populate_ep_devices() usage should be relevant here. The drm_dp_aux_register() still should to invoked before devm_of_dp_aux_populate_ep_devices(), otherwise panel->ddc adapter won't be registered.
drm_dp_aux_register() is only needed to expose the device to userspace and make the I2C adapter available to the rest of the system. But since we already know the AUX and I2C adapter, we can use it directly without doing a separate lookup. drm_dp_aux_init() should be enough to set the adapter up to work for what we need.
See also the kerneldoc for drm_dp_aux_register() where this is described in a bit more detail.
Alright, so you fixed it by removing the ddc-i2c-bus phandles and I2C DDC will work properly anyways with that on v5.16.
But the aux-bus usage still is irrelevant for the fix. Let's not use it then.
The panel->ddc isn't used by the new panel-edp driver unless panel is compatible with "edp-panel". Hence the generic_edp_panel_probe() should either fail or crash for a such "edp-panel" since panel->ddc isn't fully instantiated, AFAICS.
I've tested this and it works fine on Venice 2. Since that was the reference design for Nyan, I suspect that Nyan's will also work.
It'd be great if Thomas or anyone else with access to a Nyan could test this to verify that.
There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, 2023, hence we need to either use:
Approach #1:
- apply my variant of the fix
- backport it to v5.15
- apply your variant without aux-bus, replacing my fix on 5.16+
Although, I see that it doesn't make much sense to say "your variant without aux-bus". "Remove ddc-i2c-bus phandles from DTs" will be better.
Or
Approach #2:
- remove ddc-i2c-bus phandles in DTs
- backport (?) it to v5.15
- apply your variant without aux-bus
Or
Approach #3:
- ignore v5.15 and keep it screwed
- apply your variant as is
Which approach will you prefer?
I'm not happy that older DTBs will be broken. Can we do better about it?
Is it possible to patch DT in the code by removing the ddc-i2c-bus phandle?
Or can we patch panel-simple on 5.15 and panel-edp on 5.16, making these drivers to skip ddc-i2c-bus on Tegra+eDP? The eDP driver fixup will be trivial, fixing older panel-simple will be more invasive.
I think the best solution will be to use Approach #1 and in the end complete it with this panel-edp workaround below. This approach will have minimal code impact on 5.16+ kernels and will keep older DTBs working. Are you okay with this?
diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c index 176ef0c3cc1d..4e5b84324659 100644 --- a/drivers/gpu/drm/panel/panel-edp.c +++ b/drivers/gpu/drm/panel/panel-edp.c @@ -793,7 +793,11 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc, return err; }
- ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
- if (of_machine_is_compatible("nvidia,tegra124"))
ddc = NULL;- else
ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);- if (ddc) { panel->ddc = of_find_i2c_adapter_by_node(ddc); of_node_put(ddc);
Another alternative that may work is to check whether ddc-i2c-bus and DPAUX use the same node.
diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c index 176ef0c3cc1d..c8cf5bc3d148 100644 --- a/drivers/gpu/drm/panel/panel-edp.c +++ b/drivers/gpu/drm/panel/panel-edp.c @@ -794,7 +794,7 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc, }
ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0); - if (ddc) { + if (ddc && ddc != aux->dev->of_node) { panel->ddc = of_find_i2c_adapter_by_node(ddc); of_node_put(ddc);
20.12.2021 19:55, Dmitry Osipenko пишет:
20.12.2021 19:12, Dmitry Osipenko пишет:
20.12.2021 18:27, Thierry Reding пишет:
On Mon, Dec 20, 2021 at 05:45:41PM +0300, Dmitry Osipenko wrote:
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Hi,
this is an alternative proposal to fix panel support on Venice 2 and Nyan. Dmitry had proposed a different solution that involved reverting the I2C/DDC registration order and would complicate things by breaking the encapsulation of the driver by introducing a global (though locally scoped) variable[0].
This set of patches avoids that by using the recently introduced DP AUX bus infrastructure. The result is that the changes are actually less intrusive and not a step back. Instead they nicely remove the circular dependency that previously existed and caused these issues in the first place.
To be fair, this is not perfect either because it requires a device tree change and hence isn't technically backwards-compatible. However, given that the original device tree was badly broken in the first place, I think we can make an exception, especially since it is not generally a problem to update device trees on the affected devices.
Secondly, this relies on infrastructure that was introduced in v5.15 and therefore will be difficult to backport beyond that. However, since this functionality has been broken since v5.13 and all of the kernel versions between that and v5.15 are EOL anyway, there isn't much that we can do to fix the interim versions anyway.
Adding Doug and Laurent since they originally designed the AUX bus patches in case they see anything in here that would be objectionable.
Thierry
Thierry Reding (2): drm/tegra: dpaux: Populate AUX bus ARM: tegra: Move panels to AUX bus
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 5 files changed, 33 insertions(+), 19 deletions(-)
It should "work" since you removed the ddc-i2c-bus phandle from the panel nodes, and thus, panel->ddc won't be used during panel-edp driver probe. But this looks like a hack rather than a fix.
The AUX ->ddc will be used for panel->ddc if the ddc-i2c-bus property is not specified. And that makes perfect sense because we'd basically just be pointing back to the AUX node anyway.
I'm not sure why and how devm_of_dp_aux_populate_ep_devices() usage should be relevant here. The drm_dp_aux_register() still should to invoked before devm_of_dp_aux_populate_ep_devices(), otherwise panel->ddc adapter won't be registered.
drm_dp_aux_register() is only needed to expose the device to userspace and make the I2C adapter available to the rest of the system. But since we already know the AUX and I2C adapter, we can use it directly without doing a separate lookup. drm_dp_aux_init() should be enough to set the adapter up to work for what we need.
See also the kerneldoc for drm_dp_aux_register() where this is described in a bit more detail.
Alright, so you fixed it by removing the ddc-i2c-bus phandles and I2C DDC will work properly anyways with that on v5.16.
But the aux-bus usage still is irrelevant for the fix. Let's not use it then.
The panel->ddc isn't used by the new panel-edp driver unless panel is compatible with "edp-panel". Hence the generic_edp_panel_probe() should either fail or crash for a such "edp-panel" since panel->ddc isn't fully instantiated, AFAICS.
I've tested this and it works fine on Venice 2. Since that was the reference design for Nyan, I suspect that Nyan's will also work.
It'd be great if Thomas or anyone else with access to a Nyan could test this to verify that.
There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, 2023, hence we need to either use:
Approach #1:
- apply my variant of the fix
- backport it to v5.15
- apply your variant without aux-bus, replacing my fix on 5.16+
Although, I see that it doesn't make much sense to say "your variant without aux-bus". "Remove ddc-i2c-bus phandles from DTs" will be better.
Or
Approach #2:
- remove ddc-i2c-bus phandles in DTs
- backport (?) it to v5.15
- apply your variant without aux-bus
Or
Approach #3:
- ignore v5.15 and keep it screwed
- apply your variant as is
Which approach will you prefer?
I'm not happy that older DTBs will be broken. Can we do better about it?
Is it possible to patch DT in the code by removing the ddc-i2c-bus phandle?
Or can we patch panel-simple on 5.15 and panel-edp on 5.16, making these drivers to skip ddc-i2c-bus on Tegra+eDP? The eDP driver fixup will be trivial, fixing older panel-simple will be more invasive.
I think the best solution will be to use Approach #1 and in the end complete it with this panel-edp workaround below. This approach will have minimal code impact on 5.16+ kernels and will keep older DTBs working. Are you okay with this?
diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c index 176ef0c3cc1d..4e5b84324659 100644 --- a/drivers/gpu/drm/panel/panel-edp.c +++ b/drivers/gpu/drm/panel/panel-edp.c @@ -793,7 +793,11 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc, return err; }
- ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
- if (of_machine_is_compatible("nvidia,tegra124"))
ddc = NULL;- else
ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);- if (ddc) { panel->ddc = of_find_i2c_adapter_by_node(ddc); of_node_put(ddc);
Another alternative that may work is to check whether ddc-i2c-bus and DPAUX use the same node.
diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c index 176ef0c3cc1d..c8cf5bc3d148 100644 --- a/drivers/gpu/drm/panel/panel-edp.c +++ b/drivers/gpu/drm/panel/panel-edp.c @@ -794,7 +794,7 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc, }
ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
- if (ddc) {
- if (ddc && ddc != aux->dev->of_node) { panel->ddc = of_find_i2c_adapter_by_node(ddc); of_node_put(ddc);
I see now that the aux pointer should be populated only if aux-bus is used, so this won't work.
On Mon, Dec 20, 2021 at 07:12:03PM +0300, Dmitry Osipenko wrote:
20.12.2021 18:27, Thierry Reding пишет:
On Mon, Dec 20, 2021 at 05:45:41PM +0300, Dmitry Osipenko wrote:
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Hi,
this is an alternative proposal to fix panel support on Venice 2 and Nyan. Dmitry had proposed a different solution that involved reverting the I2C/DDC registration order and would complicate things by breaking the encapsulation of the driver by introducing a global (though locally scoped) variable[0].
This set of patches avoids that by using the recently introduced DP AUX bus infrastructure. The result is that the changes are actually less intrusive and not a step back. Instead they nicely remove the circular dependency that previously existed and caused these issues in the first place.
To be fair, this is not perfect either because it requires a device tree change and hence isn't technically backwards-compatible. However, given that the original device tree was badly broken in the first place, I think we can make an exception, especially since it is not generally a problem to update device trees on the affected devices.
Secondly, this relies on infrastructure that was introduced in v5.15 and therefore will be difficult to backport beyond that. However, since this functionality has been broken since v5.13 and all of the kernel versions between that and v5.15 are EOL anyway, there isn't much that we can do to fix the interim versions anyway.
Adding Doug and Laurent since they originally designed the AUX bus patches in case they see anything in here that would be objectionable.
Thierry
Thierry Reding (2): drm/tegra: dpaux: Populate AUX bus ARM: tegra: Move panels to AUX bus
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 5 files changed, 33 insertions(+), 19 deletions(-)
It should "work" since you removed the ddc-i2c-bus phandle from the panel nodes, and thus, panel->ddc won't be used during panel-edp driver probe. But this looks like a hack rather than a fix.
The AUX ->ddc will be used for panel->ddc if the ddc-i2c-bus property is not specified. And that makes perfect sense because we'd basically just be pointing back to the AUX node anyway.
I'm not sure why and how devm_of_dp_aux_populate_ep_devices() usage should be relevant here. The drm_dp_aux_register() still should to invoked before devm_of_dp_aux_populate_ep_devices(), otherwise panel->ddc adapter won't be registered.
drm_dp_aux_register() is only needed to expose the device to userspace and make the I2C adapter available to the rest of the system. But since we already know the AUX and I2C adapter, we can use it directly without doing a separate lookup. drm_dp_aux_init() should be enough to set the adapter up to work for what we need.
See also the kerneldoc for drm_dp_aux_register() where this is described in a bit more detail.
Alright, so you fixed it by removing the ddc-i2c-bus phandles and I2C DDC will work properly anyways with that on v5.16.
But the aux-bus usage still is irrelevant for the fix. Let's not use it then.
Yes, it's completely relevant because it essentially replaces the I2C DDC. With the AUX bus, the AUX and hence the I2C DDC can be implied from the bus' parent.
The panel->ddc isn't used by the new panel-edp driver unless panel is compatible with "edp-panel". Hence the generic_edp_panel_probe() should either fail or crash for a such "edp-panel" since panel->ddc isn't fully instantiated, AFAICS.
I've tested this and it works fine on Venice 2. Since that was the reference design for Nyan, I suspect that Nyan's will also work.
It'd be great if Thomas or anyone else with access to a Nyan could test this to verify that.
There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, 2023, hence we need to either use:
All the (at least relevant) functionality that is in panel-edp was in panel-simple before it was moved to panel-edp. I've backported this set of patches to v5.15 and it works just fine there.
Thierry
21.12.2021 13:58, Thierry Reding пишет: ..
The panel->ddc isn't used by the new panel-edp driver unless panel is compatible with "edp-panel". Hence the generic_edp_panel_probe() should either fail or crash for a such "edp-panel" since panel->ddc isn't fully instantiated, AFAICS.
I've tested this and it works fine on Venice 2. Since that was the reference design for Nyan, I suspect that Nyan's will also work.
It'd be great if Thomas or anyone else with access to a Nyan could test this to verify that.
There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, 2023, hence we need to either use:
All the (at least relevant) functionality that is in panel-edp was in panel-simple before it was moved to panel-edp. I've backported this set of patches to v5.15 and it works just fine there.
Will we be able to add patch to bypass the panel's DT ddc-i2c-bus on Nyan to keep the older DTBs working?
On Tue, Dec 21, 2021 at 06:47:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 13:58, Thierry Reding пишет: ..
The panel->ddc isn't used by the new panel-edp driver unless panel is compatible with "edp-panel". Hence the generic_edp_panel_probe() should either fail or crash for a such "edp-panel" since panel->ddc isn't fully instantiated, AFAICS.
I've tested this and it works fine on Venice 2. Since that was the reference design for Nyan, I suspect that Nyan's will also work.
It'd be great if Thomas or anyone else with access to a Nyan could test this to verify that.
There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, 2023, hence we need to either use:
All the (at least relevant) functionality that is in panel-edp was in panel-simple before it was moved to panel-edp. I've backported this set of patches to v5.15 and it works just fine there.
Will we be able to add patch to bypass the panel's DT ddc-i2c-bus on Nyan to keep the older DTBs working?
I don't see why we would want to do that. It's quite clear that the DTB is buggy in this case and we have a more accurate way to describe what's really there in hardware. In addition that more accurate representation also gets rid of a bug. Obviously because the bug is caused by the previous representation that was not accurate.
Given that we can easily replace the DTBs on these devices there's no reason to make this any more complicated than it has to be.
Thierry
21.12.2021 19:17, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 06:47:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 13:58, Thierry Reding пишет: ..
The panel->ddc isn't used by the new panel-edp driver unless panel is compatible with "edp-panel". Hence the generic_edp_panel_probe() should either fail or crash for a such "edp-panel" since panel->ddc isn't fully instantiated, AFAICS.
I've tested this and it works fine on Venice 2. Since that was the reference design for Nyan, I suspect that Nyan's will also work.
It'd be great if Thomas or anyone else with access to a Nyan could test this to verify that.
There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, 2023, hence we need to either use:
All the (at least relevant) functionality that is in panel-edp was in panel-simple before it was moved to panel-edp. I've backported this set of patches to v5.15 and it works just fine there.
Will we be able to add patch to bypass the panel's DT ddc-i2c-bus on Nyan to keep the older DTBs working?
I don't see why we would want to do that. It's quite clear that the DTB is buggy in this case and we have a more accurate way to describe what's really there in hardware. In addition that more accurate representation also gets rid of a bug. Obviously because the bug is caused by the previous representation that was not accurate.
Given that we can easily replace the DTBs on these devices there's no reason to make this any more complicated than it has to be.
Don't you care about normal people at all? Do you assume that everyone must to be a kernel developer to be able to use Tegra devices? :/
It's not a problem for you to figure out why display is broken, for other people it's a problem. Usually nobody will update DTB without a well known reason, instead device will be dusted on a shelf. In the end you won't have any users at all.
On Tue, Dec 21, 2021 at 07:45:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 19:17, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 06:47:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 13:58, Thierry Reding пишет: ..
> The panel->ddc isn't used by the new panel-edp driver unless panel is > compatible with "edp-panel". Hence the generic_edp_panel_probe() should > either fail or crash for a such "edp-panel" since panel->ddc isn't fully > instantiated, AFAICS.
I've tested this and it works fine on Venice 2. Since that was the reference design for Nyan, I suspect that Nyan's will also work.
It'd be great if Thomas or anyone else with access to a Nyan could test this to verify that.
There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, 2023, hence we need to either use:
All the (at least relevant) functionality that is in panel-edp was in panel-simple before it was moved to panel-edp. I've backported this set of patches to v5.15 and it works just fine there.
Will we be able to add patch to bypass the panel's DT ddc-i2c-bus on Nyan to keep the older DTBs working?
I don't see why we would want to do that. It's quite clear that the DTB is buggy in this case and we have a more accurate way to describe what's really there in hardware. In addition that more accurate representation also gets rid of a bug. Obviously because the bug is caused by the previous representation that was not accurate.
Given that we can easily replace the DTBs on these devices there's no reason to make this any more complicated than it has to be.
Don't you care about normal people at all? Do you assume that everyone must to be a kernel developer to be able to use Tegra devices? :/
If you know how to install a custom kernel you also know how to replace the DTB on these devices.
For everyone else, once these patches are merged upstream and distributions start shipping the new version, they will get this automatically by updating their kernel package since most distributions actually ship the DTB files as part of that.
It's not a problem for you to figure out why display is broken, for other people it's a problem. Usually nobody will update DTB without a well known reason, instead device will be dusted on a shelf. In the end you won't have any users at all.
Most "normal" people aren't even going to notice that their DTB is going to be updated. They would actually have to do extra work *not* to update it.
Thierry
21.12.2021 21:01, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 07:45:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 19:17, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 06:47:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 13:58, Thierry Reding пишет: ..
>> The panel->ddc isn't used by the new panel-edp driver unless panel is >> compatible with "edp-panel". Hence the generic_edp_panel_probe() should >> either fail or crash for a such "edp-panel" since panel->ddc isn't fully >> instantiated, AFAICS. > > I've tested this and it works fine on Venice 2. Since that was the > reference design for Nyan, I suspect that Nyan's will also work. > > It'd be great if Thomas or anyone else with access to a Nyan could > test this to verify that.
There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, 2023, hence we need to either use:
All the (at least relevant) functionality that is in panel-edp was in panel-simple before it was moved to panel-edp. I've backported this set of patches to v5.15 and it works just fine there.
Will we be able to add patch to bypass the panel's DT ddc-i2c-bus on Nyan to keep the older DTBs working?
I don't see why we would want to do that. It's quite clear that the DTB is buggy in this case and we have a more accurate way to describe what's really there in hardware. In addition that more accurate representation also gets rid of a bug. Obviously because the bug is caused by the previous representation that was not accurate.
Given that we can easily replace the DTBs on these devices there's no reason to make this any more complicated than it has to be.
Don't you care about normal people at all? Do you assume that everyone must to be a kernel developer to be able to use Tegra devices? :/
If you know how to install a custom kernel you also know how to replace the DTB on these devices.
For everyone else, once these patches are merged upstream and distributions start shipping the new version, they will get this automatically by updating their kernel package since most distributions actually ship the DTB files as part of that.
It's not a problem for you to figure out why display is broken, for other people it's a problem. Usually nobody will update DTB without a well known reason, instead device will be dusted on a shelf. In the end you won't have any users at all.
Most "normal" people aren't even going to notice that their DTB is going to be updated. They would actually have to do extra work *not* to update it.
My past experience tells that your assumption is incorrect. There are quite a lot of people who will update kernel, but not DTB.
ARM devices have endless variations of bootloaders and individual quirks required for a successful installation of a kernel. Kernel update by distro usually isn't a thing on ARM.
On Wed, Dec 22, 2021 at 06:01:26AM +0300, Dmitry Osipenko wrote:
21.12.2021 21:01, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 07:45:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 19:17, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 06:47:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 13:58, Thierry Reding пишет: ..
>>> The panel->ddc isn't used by the new panel-edp driver unless panel is >>> compatible with "edp-panel". Hence the generic_edp_panel_probe() should >>> either fail or crash for a such "edp-panel" since panel->ddc isn't fully >>> instantiated, AFAICS. >> >> I've tested this and it works fine on Venice 2. Since that was the >> reference design for Nyan, I suspect that Nyan's will also work. >> >> It'd be great if Thomas or anyone else with access to a Nyan could >> test this to verify that. > > There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, > 2023, hence we need to either use:
All the (at least relevant) functionality that is in panel-edp was in panel-simple before it was moved to panel-edp. I've backported this set of patches to v5.15 and it works just fine there.
Will we be able to add patch to bypass the panel's DT ddc-i2c-bus on Nyan to keep the older DTBs working?
I don't see why we would want to do that. It's quite clear that the DTB is buggy in this case and we have a more accurate way to describe what's really there in hardware. In addition that more accurate representation also gets rid of a bug. Obviously because the bug is caused by the previous representation that was not accurate.
Given that we can easily replace the DTBs on these devices there's no reason to make this any more complicated than it has to be.
Don't you care about normal people at all? Do you assume that everyone must to be a kernel developer to be able to use Tegra devices? :/
If you know how to install a custom kernel you also know how to replace the DTB on these devices.
For everyone else, once these patches are merged upstream and distributions start shipping the new version, they will get this automatically by updating their kernel package since most distributions actually ship the DTB files as part of that.
It's not a problem for you to figure out why display is broken, for other people it's a problem. Usually nobody will update DTB without a well known reason, instead device will be dusted on a shelf. In the end you won't have any users at all.
Most "normal" people aren't even going to notice that their DTB is going to be updated. They would actually have to do extra work *not* to update it.
My past experience tells that your assumption is incorrect. There are quite a lot of people who will update kernel, but not DTB.
People that do this will have to do it manually because most distributions I know of will actually ship the DTBs. If they know how to update the kernel separately, I'm sure they will manage to update the DTB as well. It's really not more complicated that updating the kernel image.
ARM devices have endless variations of bootloaders and individual quirks required for a successful installation of a kernel. Kernel update by distro usually isn't a thing on ARM.
I'm not sure what distribution you have been using, but the ones that I'm familiar with all install the DTBs along with the kernel. Most Tegra devices (newer ones at least) do also support booting with U-Boot which supports standard ways to boot a system (which were co-developed with distributions precisely so that it would become easier for users to keep their systems up-to-date), so there's really nothing magical anyone should need to do in order to get an updated DTB along with the updated kernel.
It's a simple fact that sometimes a DTB contains a bug and we have to fix it.
In general we try to fix things up in the driver code when reasonable so that people don't have to update the DTB. This is for the (mostly hypo- thetical) case where updating the DTB is not possible or very complicated.
However, that's not the case on the Venice 2 or Nyan boards. And looking at the alternative in this case, I don't think it's reasonable compared to just fixing the problem at the root, which is in the DTB.
Thierry
22.12.2021 14:53, Thierry Reding пишет:
On Wed, Dec 22, 2021 at 06:01:26AM +0300, Dmitry Osipenko wrote:
21.12.2021 21:01, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 07:45:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 19:17, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 06:47:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 13:58, Thierry Reding пишет: .. >>>> The panel->ddc isn't used by the new panel-edp driver unless panel is >>>> compatible with "edp-panel". Hence the generic_edp_panel_probe() should >>>> either fail or crash for a such "edp-panel" since panel->ddc isn't fully >>>> instantiated, AFAICS. >>> >>> I've tested this and it works fine on Venice 2. Since that was the >>> reference design for Nyan, I suspect that Nyan's will also work. >>> >>> It'd be great if Thomas or anyone else with access to a Nyan could >>> test this to verify that. >> >> There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, >> 2023, hence we need to either use: > > All the (at least relevant) functionality that is in panel-edp was in > panel-simple before it was moved to panel-edp. I've backported this set > of patches to v5.15 and it works just fine there.
Will we be able to add patch to bypass the panel's DT ddc-i2c-bus on Nyan to keep the older DTBs working?
I don't see why we would want to do that. It's quite clear that the DTB is buggy in this case and we have a more accurate way to describe what's really there in hardware. In addition that more accurate representation also gets rid of a bug. Obviously because the bug is caused by the previous representation that was not accurate.
Given that we can easily replace the DTBs on these devices there's no reason to make this any more complicated than it has to be.
Don't you care about normal people at all? Do you assume that everyone must to be a kernel developer to be able to use Tegra devices? :/
If you know how to install a custom kernel you also know how to replace the DTB on these devices.
For everyone else, once these patches are merged upstream and distributions start shipping the new version, they will get this automatically by updating their kernel package since most distributions actually ship the DTB files as part of that.
It's not a problem for you to figure out why display is broken, for other people it's a problem. Usually nobody will update DTB without a well known reason, instead device will be dusted on a shelf. In the end you won't have any users at all.
Most "normal" people aren't even going to notice that their DTB is going to be updated. They would actually have to do extra work *not* to update it.
My past experience tells that your assumption is incorrect. There are quite a lot of people who will update kernel, but not DTB.
People that do this will have to do it manually because most distributions I know of will actually ship the DTBs. If they know how to update the kernel separately, I'm sure they will manage to update the DTB as well. It's really not more complicated that updating the kernel image.
ARM devices have endless variations of bootloaders and individual quirks required for a successful installation of a kernel. Kernel update by distro usually isn't a thing on ARM.
I'm not sure what distribution you have been using, but the ones that I'm familiar with all install the DTBs along with the kernel. Most Tegra devices (newer ones at least) do also support booting with U-Boot which supports standard ways to boot a system (which were co-developed with distributions precisely so that it would become easier for users to keep their systems up-to-date), so there's really nothing magical anyone should need to do in order to get an updated DTB along with the updated kernel.
It's a simple fact that sometimes a DTB contains a bug and we have to fix it.
In general we try to fix things up in the driver code when reasonable so that people don't have to update the DTB. This is for the (mostly hypo- thetical) case where updating the DTB is not possible or very complicated.
However, that's not the case on the Venice 2 or Nyan boards. And looking at the alternative in this case, I don't think it's reasonable compared to just fixing the problem at the root, which is in the DTB.
My understanding that U-Boot isn't the only available bootloader option for Nyan. I don't feel happy about the ABI breakage, but in the same time don't feel very strong about the need to care about it in the case of Nyan since its DT already had a preexisting problem with the wrong panel model used for the FHD model. The decision will be on your conscience :)
Hi,
On Wed, Dec 22, 2021 at 11:26 AM Dmitry Osipenko digetx@gmail.com wrote:
22.12.2021 14:53, Thierry Reding пишет:
On Wed, Dec 22, 2021 at 06:01:26AM +0300, Dmitry Osipenko wrote:
21.12.2021 21:01, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 07:45:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 19:17, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 06:47:31PM +0300, Dmitry Osipenko wrote: > 21.12.2021 13:58, Thierry Reding пишет: > .. >>>>> The panel->ddc isn't used by the new panel-edp driver unless panel is >>>>> compatible with "edp-panel". Hence the generic_edp_panel_probe() should >>>>> either fail or crash for a such "edp-panel" since panel->ddc isn't fully >>>>> instantiated, AFAICS. >>>> >>>> I've tested this and it works fine on Venice 2. Since that was the >>>> reference design for Nyan, I suspect that Nyan's will also work. >>>> >>>> It'd be great if Thomas or anyone else with access to a Nyan could >>>> test this to verify that. >>> >>> There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, >>> 2023, hence we need to either use: >> >> All the (at least relevant) functionality that is in panel-edp was in >> panel-simple before it was moved to panel-edp. I've backported this set >> of patches to v5.15 and it works just fine there. > > Will we be able to add patch to bypass the panel's DT ddc-i2c-bus on > Nyan to keep the older DTBs working?
I don't see why we would want to do that. It's quite clear that the DTB is buggy in this case and we have a more accurate way to describe what's really there in hardware. In addition that more accurate representation also gets rid of a bug. Obviously because the bug is caused by the previous representation that was not accurate.
Given that we can easily replace the DTBs on these devices there's no reason to make this any more complicated than it has to be.
Don't you care about normal people at all? Do you assume that everyone must to be a kernel developer to be able to use Tegra devices? :/
If you know how to install a custom kernel you also know how to replace the DTB on these devices.
For everyone else, once these patches are merged upstream and distributions start shipping the new version, they will get this automatically by updating their kernel package since most distributions actually ship the DTB files as part of that.
It's not a problem for you to figure out why display is broken, for other people it's a problem. Usually nobody will update DTB without a well known reason, instead device will be dusted on a shelf. In the end you won't have any users at all.
Most "normal" people aren't even going to notice that their DTB is going to be updated. They would actually have to do extra work *not* to update it.
My past experience tells that your assumption is incorrect. There are quite a lot of people who will update kernel, but not DTB.
People that do this will have to do it manually because most distributions I know of will actually ship the DTBs. If they know how to update the kernel separately, I'm sure they will manage to update the DTB as well. It's really not more complicated that updating the kernel image.
ARM devices have endless variations of bootloaders and individual quirks required for a successful installation of a kernel. Kernel update by distro usually isn't a thing on ARM.
I'm not sure what distribution you have been using, but the ones that I'm familiar with all install the DTBs along with the kernel. Most Tegra devices (newer ones at least) do also support booting with U-Boot which supports standard ways to boot a system (which were co-developed with distributions precisely so that it would become easier for users to keep their systems up-to-date), so there's really nothing magical anyone should need to do in order to get an updated DTB along with the updated kernel.
It's a simple fact that sometimes a DTB contains a bug and we have to fix it.
In general we try to fix things up in the driver code when reasonable so that people don't have to update the DTB. This is for the (mostly hypo- thetical) case where updating the DTB is not possible or very complicated.
However, that's not the case on the Venice 2 or Nyan boards. And looking at the alternative in this case, I don't think it's reasonable compared to just fixing the problem at the root, which is in the DTB.
My understanding that U-Boot isn't the only available bootloader option for Nyan. I don't feel happy about the ABI breakage, but in the same time don't feel very strong about the need to care about it in the case of Nyan since its DT already had a preexisting problem with the wrong panel model used for the FHD model. The decision will be on your conscience :)
Maybe I should stand back to avoid getting hit by tomatoes, but IMO it's a terrible idea to try to update devices trees separately from kernels for any sufficiently complicated device. I won't stop you from shooting yourself in the foot, but I also certainly wouldn't encourage it. I've always said that I'll accept that this is something to really worry about when we land chunk of "device tree fixup" code that runs in early boot to fix all the broken device trees out there. All ARM Chrome OS devices that have ever shipped all bundle device trees together with the kernel (they bundle a whole pile of them and the bootloader picks the right one based on model). Sure, someone could decide to bake one into their bootloader but, even aside from this case, there are sometimes bugs in device trees and they need to get fixed. Updating your kernel without your device tree is just bad juju IMO.
I'll let you and Thierry figure out what you want to do for 5.15. In the Chrome OS 5.15 kernel tree we simply backported all the edp-panel stuff, which was fairly clean. I even backported all that stuff to 5.4, but it was decidedly more complex...
-Doug
06.01.2022 04:11, Doug Anderson пишет:
Hi,
On Wed, Dec 22, 2021 at 11:26 AM Dmitry Osipenko digetx@gmail.com wrote:
22.12.2021 14:53, Thierry Reding пишет:
On Wed, Dec 22, 2021 at 06:01:26AM +0300, Dmitry Osipenko wrote:
21.12.2021 21:01, Thierry Reding пишет:
On Tue, Dec 21, 2021 at 07:45:31PM +0300, Dmitry Osipenko wrote:
21.12.2021 19:17, Thierry Reding пишет: > On Tue, Dec 21, 2021 at 06:47:31PM +0300, Dmitry Osipenko wrote: >> 21.12.2021 13:58, Thierry Reding пишет: >> .. >>>>>> The panel->ddc isn't used by the new panel-edp driver unless panel is >>>>>> compatible with "edp-panel". Hence the generic_edp_panel_probe() should >>>>>> either fail or crash for a such "edp-panel" since panel->ddc isn't fully >>>>>> instantiated, AFAICS. >>>>> >>>>> I've tested this and it works fine on Venice 2. Since that was the >>>>> reference design for Nyan, I suspect that Nyan's will also work. >>>>> >>>>> It'd be great if Thomas or anyone else with access to a Nyan could >>>>> test this to verify that. >>>> >>>> There is no panel-edp driver in the v5.15. The EOL of v5.15 is Oct, >>>> 2023, hence we need to either use: >>> >>> All the (at least relevant) functionality that is in panel-edp was in >>> panel-simple before it was moved to panel-edp. I've backported this set >>> of patches to v5.15 and it works just fine there. >> >> Will we be able to add patch to bypass the panel's DT ddc-i2c-bus on >> Nyan to keep the older DTBs working? > > I don't see why we would want to do that. It's quite clear that the DTB > is buggy in this case and we have a more accurate way to describe what's > really there in hardware. In addition that more accurate representation > also gets rid of a bug. Obviously because the bug is caused by the > previous representation that was not accurate. > > Given that we can easily replace the DTBs on these devices there's no > reason to make this any more complicated than it has to be.
Don't you care about normal people at all? Do you assume that everyone must to be a kernel developer to be able to use Tegra devices? :/
If you know how to install a custom kernel you also know how to replace the DTB on these devices.
For everyone else, once these patches are merged upstream and distributions start shipping the new version, they will get this automatically by updating their kernel package since most distributions actually ship the DTB files as part of that.
It's not a problem for you to figure out why display is broken, for other people it's a problem. Usually nobody will update DTB without a well known reason, instead device will be dusted on a shelf. In the end you won't have any users at all.
Most "normal" people aren't even going to notice that their DTB is going to be updated. They would actually have to do extra work *not* to update it.
My past experience tells that your assumption is incorrect. There are quite a lot of people who will update kernel, but not DTB.
People that do this will have to do it manually because most distributions I know of will actually ship the DTBs. If they know how to update the kernel separately, I'm sure they will manage to update the DTB as well. It's really not more complicated that updating the kernel image.
ARM devices have endless variations of bootloaders and individual quirks required for a successful installation of a kernel. Kernel update by distro usually isn't a thing on ARM.
I'm not sure what distribution you have been using, but the ones that I'm familiar with all install the DTBs along with the kernel. Most Tegra devices (newer ones at least) do also support booting with U-Boot which supports standard ways to boot a system (which were co-developed with distributions precisely so that it would become easier for users to keep their systems up-to-date), so there's really nothing magical anyone should need to do in order to get an updated DTB along with the updated kernel.
It's a simple fact that sometimes a DTB contains a bug and we have to fix it.
In general we try to fix things up in the driver code when reasonable so that people don't have to update the DTB. This is for the (mostly hypo- thetical) case where updating the DTB is not possible or very complicated.
However, that's not the case on the Venice 2 or Nyan boards. And looking at the alternative in this case, I don't think it's reasonable compared to just fixing the problem at the root, which is in the DTB.
My understanding that U-Boot isn't the only available bootloader option for Nyan. I don't feel happy about the ABI breakage, but in the same time don't feel very strong about the need to care about it in the case of Nyan since its DT already had a preexisting problem with the wrong panel model used for the FHD model. The decision will be on your conscience :)
Maybe I should stand back to avoid getting hit by tomatoes, but IMO it's a terrible idea to try to update devices trees separately from kernels for any sufficiently complicated device. I won't stop you from shooting yourself in the foot, but I also certainly wouldn't encourage it. I've always said that I'll accept that this is something to really worry about when we land chunk of "device tree fixup" code that runs in early boot to fix all the broken device trees out there. All ARM Chrome OS devices that have ever shipped all bundle device trees together with the kernel (they bundle a whole pile of them and the bootloader picks the right one based on model). Sure, someone could decide to bake one into their bootloader but, even aside from this case, there are sometimes bugs in device trees and they need to get fixed. Updating your kernel without your device tree is just bad juju IMO.
I'll let you and Thierry figure out what you want to do for 5.15. In the Chrome OS 5.15 kernel tree we simply backported all the edp-panel stuff, which was fairly clean. I even backported all that stuff to 5.4, but it was decidedly more complex...
Chrome OS is a commercial product, while here we are talking about normal (non-kernel/developer) people. It's incorrect to compare home hackers with professional developers/products, IMO.
If we could keep older DTBs working without much effort, then will be great. If not, maybe not a big deal.
I suggested variants of preserving the older DTBs and leaving it up to Thierry to decide what to do.
20.12.2021 13:48, Thierry Reding пишет:
From: Thierry Reding treding@nvidia.com
Hi,
this is an alternative proposal to fix panel support on Venice 2 and Nyan. Dmitry had proposed a different solution that involved reverting the I2C/DDC registration order and would complicate things by breaking the encapsulation of the driver by introducing a global (though locally scoped) variable[0].
This set of patches avoids that by using the recently introduced DP AUX bus infrastructure. The result is that the changes are actually less intrusive and not a step back. Instead they nicely remove the circular dependency that previously existed and caused these issues in the first place.
To be fair, this is not perfect either because it requires a device tree change and hence isn't technically backwards-compatible. However, given that the original device tree was badly broken in the first place, I think we can make an exception, especially since it is not generally a problem to update device trees on the affected devices.
Secondly, this relies on infrastructure that was introduced in v5.15 and therefore will be difficult to backport beyond that. However, since this functionality has been broken since v5.13 and all of the kernel versions between that and v5.15 are EOL anyway, there isn't much that we can do to fix the interim versions anyway.
Adding Doug and Laurent since they originally designed the AUX bus patches in case they see anything in here that would be objectionable.
Thierry
Thierry Reding (2): drm/tegra: dpaux: Populate AUX bus ARM: tegra: Move panels to AUX bus
arch/arm/boot/dts/tegra124-nyan-big.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------ arch/arm/boot/dts/tegra124-venice2.dts | 14 +++++++------- drivers/gpu/drm/tegra/Kconfig | 1 + drivers/gpu/drm/tegra/dpaux.c | 7 +++++++ 5 files changed, 33 insertions(+), 19 deletions(-)
Will we see the v2 anytime soon?
dri-devel@lists.freedesktop.org
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Dmitry Osipenko -
Doug Anderson -
Thierry Reding