On Tue, 15 Sep 2020 21:40:40 +0200, Andrzej Hajda wrote:
W dniu 14.09.2020 o 23:19, Andrzej Hajda pisze:
On 14.09.2020 22:01, Michael Tretter wrote:
On Mon, 14 Sep 2020 14:31:19 +0200, Marek Szyprowski wrote:
On 14.09.2020 10:29, Marek Szyprowski wrote:
On 11.09.2020 15:54, Michael Tretter wrote:
Make the exynos_dsi driver a full drm bridge that can be found and used from other drivers.
Other drivers can only attach to the bridge, if a mipi dsi device already attached to the bridge. This allows to defer the probe of the display pipe until the downstream bridges are available, too.
Signed-off-by: Michael Tretter m.tretter@pengutronix.de
This one (and the whole series applied) still fails on Exynos boards:
[drm] Exynos DRM: using 11c00000.fimd device for DMA mapping operations exynos-drm exynos-drm: bound 11c00000.fimd (ops fimd_component_ops) OF: graph: no port node found in /soc/dsi@11c80000 8<--- cut here --- Unable to handle kernel NULL pointer dereference at virtual address 00000084 pgd = (ptrval) [00000084] *pgd=00000000 Internal error: Oops: 5 [#1] PREEMPT SMP ARM Modules linked in: CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc4-next-20200911-00010-g417dc70d70ec #1608 Hardware name: Samsung Exynos (Flattened Device Tree) PC is at drm_bridge_attach+0x18/0x164 LR is at exynos_dsi_bind+0x88/0xa8 pc : [<c0628c08>] lr : [<c064d560>] psr: 20000013 sp : ef0dfca8 ip : 00000002 fp : c13190e0 r10: 00000000 r9 : ee46d580 r8 : c13190e0 r7 : ee438800 r6 : 00000018 r5 : ef253810 r4 : ef39e840 r3 : 00000000 r2 : 00000018 r1 : ef39e888 r0 : ef39e840 Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 4000404a DAC: 00000051 Process swapper/0 (pid: 1, stack limit = 0x(ptrval)) Stack: (0xef0dfca8 to 0xef0e0000) ... [<c0628c08>] (drm_bridge_attach) from [<c064d560>] (exynos_dsi_bind+0x88/0xa8) [<c064d560>] (exynos_dsi_bind) from [<c066a800>] (component_bind_all+0xfc/0x290) [<c066a800>] (component_bind_all) from [<c0649dc0>] (exynos_drm_bind+0xe4/0x19c) [<c0649dc0>] (exynos_drm_bind) from [<c066ad74>] (try_to_bring_up_master+0x1e4/0x2c4) [<c066ad74>] (try_to_bring_up_master) from [<c066b2b4>] (component_master_add_with_match+0xd4/0x108) [<c066b2b4>] (component_master_add_with_match) from [<c0649ae8>] (exynos_drm_platform_probe+0xe4/0x110) [<c0649ae8>] (exynos_drm_platform_probe) from [<c0674e6c>] (platform_drv_probe+0x6c/0xa4) [<c0674e6c>] (platform_drv_probe) from [<c067242c>] (really_probe+0x200/0x4fc) [<c067242c>] (really_probe) from [<c06728f0>] (driver_probe_device+0x78/0x1fc) [<c06728f0>] (driver_probe_device) from [<c0672cd8>] (device_driver_attach+0x58/0x60) [<c0672cd8>] (device_driver_attach) from [<c0672dbc>] (__driver_attach+0xdc/0x174) [<c0672dbc>] (__driver_attach) from [<c06701b4>] (bus_for_each_dev+0x68/0xb4) [<c06701b4>] (bus_for_each_dev) from [<c06714e8>] (bus_add_driver+0x158/0x214) [<c06714e8>] (bus_add_driver) from [<c0673c1c>] (driver_register+0x78/0x110) [<c0673c1c>] (driver_register) from [<c0649ca8>] (exynos_drm_init+0xe4/0x118) [<c0649ca8>] (exynos_drm_init) from [<c0102484>] (do_one_initcall+0x8c/0x42c) [<c0102484>] (do_one_initcall) from [<c11011c0>] (kernel_init_freeable+0x190/0x1dc) [<c11011c0>] (kernel_init_freeable) from [<c0af7880>] (kernel_init+0x8/0x118) [<c0af7880>] (kernel_init) from [<c0100114>] (ret_from_fork+0x14/0x20) Exception stack(0xef0dffb0 to 0xef0dfff8) ... ---[ end trace ee27f313f9ed9da1 ]---
# arm-linux-gnueabi-addr2line -e vmlinux c0628c08 drivers/gpu/drm/drm_bridge.c:184 (discriminator 1)
I will try to debug it a bit more today.
The above crash has been caused by lack of in_bridge initialization to NULL in exynos_dsi_bind() in this patch. However, fixing it reveals another issue:
[drm] Exynos DRM: using 11c00000.fimd device for DMA mapping operations exynos-drm exynos-drm: bound 11c00000.fimd (ops fimd_component_ops) OF: graph: no port node found in /soc/dsi@11c80000 8<--- cut here --- Unable to handle kernel NULL pointer dereference at virtual address 00000280 pgd = (ptrval) [00000280] *pgd=00000000 Internal error: Oops: 5 [#1] PREEMPT SMP ARM Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc4-next-20200911-00010-g417dc70d70ec-dirty #1613 Hardware name: Samsung Exynos (Flattened Device Tree) PC is at __mutex_lock+0x54/0xb18 LR is at lock_is_held_type+0x80/0x138 pc : [<c0afc920>] lr : [<c0af63e8>] psr: 60000013 sp : ef0dfd30 ip : 33937b74 fp : c13193c8 r10: c1208eec r9 : 00000000 r8 : ee45f808 r7 : c19561a4 r6 : 00000000 r5 : 00000000 r4 : 0000024c r3 : 00000000 r2 : 00204140 r1 : c124f13c r0 : 00000000 Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 4000404a DAC: 00000051 Process swapper/0 (pid: 1, stack limit = 0x(ptrval)) Stack: (0xef0dfd30 to 0xef0e0000) ... [<c0afc920>] (__mutex_lock) from [<c0afd400>] (mutex_lock_nested+0x1c/0x24) [<c0afd400>] (mutex_lock_nested) from [<c064d4b8>] (__exynos_dsi_host_attach+0x20/0x6c) [<c064d4b8>] (__exynos_dsi_host_attach) from [<c064d914>] (exynos_dsi_host_attach+0x70/0x194) [<c064d914>] (exynos_dsi_host_attach) from [<c0656b64>] (s6e8aa0_probe+0x1b0/0x218) [<c0656b64>] (s6e8aa0_probe) from [<c0672530>] (really_probe+0x200/0x4fc) [<c0672530>] (really_probe) from [<c06729f4>] (driver_probe_device+0x78/0x1fc) [<c06729f4>] (driver_probe_device) from [<c0672ddc>] (device_driver_attach+0x58/0x60) [<c0672ddc>] (device_driver_attach) from [<c0672ec0>] (__driver_attach+0xdc/0x174) [<c0672ec0>] (__driver_attach) from [<c06702b8>] (bus_for_each_dev+0x68/0xb4) [<c06702b8>] (bus_for_each_dev) from [<c06715ec>] (bus_add_driver+0x158/0x214) [<c06715ec>] (bus_add_driver) from [<c0673d20>] (driver_register+0x78/0x110) [<c0673d20>] (driver_register) from [<c0102484>] (do_one_initcall+0x8c/0x42c) [<c0102484>] (do_one_initcall) from [<c11011c0>] (kernel_init_freeable+0x190/0x1dc) [<c11011c0>] (kernel_init_freeable) from [<c0af7988>] (kernel_init+0x8/0x118) [<c0af7988>] (kernel_init) from [<c0100114>] (ret_from_fork+0x14/0x20) Exception stack(0xef0dffb0 to 0xef0dfff8) ... ---[ end trace c06e996ec2e8234d ]---
This means that dsi->encoder.dev is not initialized in __exynos_dsi_host_attach().
This happens, because drm_bridge_attach() in exynos_dsi_bind() returned earlier -517 (deferred probe), what causes cleanup of encoder and release of all drm resources.
Then however, the panel tries to register itself and exynos_dsi_host_attach() tries to access the released encoder (which is zeroed in drm_encoder_release) and rest of resources, what causes failure.
It looks that something is missing. Maybe mipi host has to be registered later, when bridge is ready? I have no idea how it is handled before this patch. Andrzej, could you comment it a bit?
I intentionally changed the order, because if another bridge follows in the pipeline, the probe of the drm driver has to be deferred until some bridge provides a connector. The next bridge registers itself via the host_attach function and the deferral is ensured via the bind for the bind/unbind API or the bridge_attach function otherwise.
On the other hand, the bridge does not have an encoder until the mipi device has been attached.
As a solution, the exynos dsi driver must initialize the encoder in exynos_dsi_probe instead of in exynos_dsi_bind and access the encoder via exynos_dsi instead of the bridge.
Can you try to move everything except samsung_dsim_bind from exynos_dsi_bind to exynos_dsi_probe (respectively for unbind) and report if it fixes the crash.
The original behaviour is that encoder (exynos_dsi) is registered regardless of sink presence (initially panel, later also bridge) - it avoids multiple issues with deferred probe, device driver bind/unbind and module load/unload. Appearance or disappearance of sink is reported to host nicely via DSI attach/detach callbacks - and it is reflected in drm world as change state of the connector.
Registering DSI host in bind and unregistering in unbind assures that if mipi_dsi device is attached/detached the drm device is always present - it makes device/driver binding race free and allows to avoid additional locking.
Moving DSI host registration to probe changes everything, for sure it breaks the nice feature of DSI attach/detach callbacks and apparently can cause different issues depending on device bind order.
I will try to look at the patches tomorrow and maybe I can find more constructive comments :)
As I said yesterday, exynos_dsi driver uses dsi host attach/detach callbacks to control appearance/disappearance of downstream device. It allows to:
- Safely bind/unbind different device drivers at any time and at any
order, without killing exynos_drm and/or crashing system.
- Avoid issues with late drm init - on some platforms exynos_drm device
appeared too late, due to deferred probe, and resulted in black screen in userspace.
Now if we want to convert exynos_dsi to drm_bridge I see following options:
A. Forgot about callbacks and make the exynos_drm to defer probing until exynos_dsi bridge is available, probably it will cause later exynos_drm appearance, thus probably black screen on some targets. So for sure it will be suboptimal. Making it bridge unbind safe would be another problem, but most developers do not care about it so why should we? :)
B. Try to mimic current behaviour - exynos_dsi register bridge ASAP, even if downstream devices are not yet attached, on attach/detach notify drm about it via connector status change, for this dsi_host registration should be performed from drm_bridge attach, I guess.
Option A is more standard, but is unsafe and causes other issues.
Option B keeps current behaviour.
Maybe we can have both, but I am not sure, if I am missing something:
I still prefer option A for the samsung-dsim driver, because it is more standard, simpler and avoids issues with encoders, connectors or handling hotplug.
The idea is to use two bridges in the exynos-dsi driver: One bridge in the samsung-dsim driver which implements option A and defers probing of the drm driver until the next bridge is attached. And a second bridge in the exynos_dsi that attaches to the first bridge (thus, allowing the exynos_drm device to appear) and implements the hotplug handling for notifying drm via connector status change.
The driver for the i.MX8M would use the samsung-dsim bridge without an additional bridge.
This allows the samsung-dsim driver to expose the standard behavior while the exynos_dsi may stick to the existing behavior for the exynos_drm driver.
I hope this makes sense and does not sound too crazy. It might be difficult to get the probing and mipi host/device registration correct, but I will try, if this can work.
Michael