Sometimes it's useful for users of the DP AUX bus (like panels) to be able to poll HPD. Let's add a callback that allows DP AUX busses drivers to provide this.

Suggested-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org Signed-off-by: Douglas Anderson dianders@chromium.org Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org ---

Changes in v4: - Comments now explain that we may wait longer due to debouncing. - Rebased to handle the fact that the stuct moved files.

Changes in v2: - Change is_hpd_asserted() to wait_hpd_asserted()

include/drm/display/drm_dp_helper.h | 30 +++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+)

diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h index c5f8f45511ed..db0fe9f8a612 100644 --- a/include/drm/display/drm_dp_helper.h +++ b/include/drm/display/drm_dp_helper.h @@ -389,6 +389,36 @@ struct drm_dp_aux { ssize_t (*transfer)(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg);

+ /** + * @wait_hpd_asserted: wait for HPD to be asserted + * + * This is mainly useful for eDP panels drivers to wait for an eDP + * panel to finish powering on. This is an optional function. + * + * This function will efficiently wait for the HPD signal to be + * asserted. The `wait_us` parameter that is passed in says that we + * know that the HPD signal is expected to be asserted within `wait_us` + * microseconds. This function could wait for longer than `wait_us` if + * the logic in the DP controller has a long debouncing time. The + * important thing is that if this function returns success that the + * DP controller is ready to send AUX transactions. + * + * This function returns 0 if HPD was asserted or -ETIMEDOUT if time + * expired and HPD wasn't asserted. This function should not print + * timeout errors to the log. + * + * The semantics of this function are designed to match the + * readx_poll_timeout() function. That means a `wait_us` of 0 means + * to wait forever. Like readx_poll_timeout(), this function may sleep. + * + * NOTE: this function specifically reports the state of the HPD pin + * that's associated with the DP AUX channel. This is different from + * the HPD concept in much of the rest of DRM which is more about + * physical presence of a display. For eDP, for instance, a display is + * assumed always present even if the HPD pin is deasserted. + */ + int (*wait_hpd_asserted)(struct drm_dp_aux *aux, unsigned long wait_us); + /** * @i2c_nack_count: Counts I2C NACKs, used for DP validation. */

Let's add support for being able to read the HPD pin even if it's hooked directly to the controller. This will let us take away the waiting in the AUX transfer functions of the eDP controller drivers.

Signed-off-by: Douglas Anderson dianders@chromium.org ---

Changes in v4: - Reorganized logic as per Dmitry's suggestion.

Changes in v3: - Don't check "hpd_asserted" boolean when unset. - Handle errors from gpiod_get_value_cansleep() properly.

Changes in v2: - Change is_hpd_asserted() to wait_hpd_asserted()

.../gpu/drm/panel/panel-samsung-atna33xc20.c | 51 ++++++++++++++----- 1 file changed, 38 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-samsung-atna33xc20.c b/drivers/gpu/drm/panel/panel-samsung-atna33xc20.c index 3dd10412d147..5a8b978c6415 100644 --- a/drivers/gpu/drm/panel/panel-samsung-atna33xc20.c +++ b/drivers/gpu/drm/panel/panel-samsung-atna33xc20.c @@ -19,6 +19,10 @@ #include <drm/drm_edid.h> #include <drm/drm_panel.h>

+/* T3 VCC to HPD high is max 200 ms */ +#define HPD_MAX_MS 200 +#define HPD_MAX_US (HPD_MAX_MS * 1000) + struct atana33xc20_panel { struct drm_panel base; bool prepared; @@ -30,6 +34,7 @@ struct atana33xc20_panel {

struct regulator *supply; struct gpio_desc *el_on3_gpio; + struct drm_dp_aux *aux;

struct edid *edid;

@@ -79,7 +84,7 @@ static int atana33xc20_suspend(struct device *dev) static int atana33xc20_resume(struct device *dev) { struct atana33xc20_panel *p = dev_get_drvdata(dev); - bool hpd_asserted = false; + int hpd_asserted; int ret;

/* T12 (Power off time) is min 500 ms */ @@ -90,23 +95,41 @@ static int atana33xc20_resume(struct device *dev) return ret; p->powered_on_time = ktime_get();

- /* - * Handle HPD. Note: if HPD is hooked up to a dedicated pin on the - * eDP controller then "no_hpd" will be false _and_ "hpd_gpio" will be - * NULL. It's up to the controller driver to wait for HPD after - * preparing the panel in that case. - */ if (p->no_hpd) { - /* T3 VCC to HPD high is max 200 ms */ - msleep(200); - } else if (p->hpd_gpio) { + msleep(HPD_MAX_MS); + return 0; + } + + if (p->hpd_gpio) { ret = readx_poll_timeout(gpiod_get_value_cansleep, p->hpd_gpio, hpd_asserted, hpd_asserted, - 1000, 200000); - if (!hpd_asserted) - dev_warn(dev, "Timeout waiting for HPD\n"); + 1000, HPD_MAX_US); + if (hpd_asserted < 0) + ret = hpd_asserted; + + if (ret) + dev_warn(dev, "Error waiting for HPD GPIO: %d\n", ret); + + return ret; }

+ if (p->aux->wait_hpd_asserted) { + ret = p->aux->wait_hpd_asserted(p->aux, HPD_MAX_US); + + if (ret) + dev_warn(dev, "Controller error waiting for HPD: %d\n", ret); + + return ret; + } + + /* + * Note that it's possible that no_hpd is false, hpd_gpio is + * NULL, and wait_hpd_asserted is NULL. This is because + * wait_hpd_asserted() is optional even if HPD is hooked up to + * a dedicated pin on the eDP controller. In this case we just + * assume that the controller driver will wait for HPD at the + * right times. + */ return 0; }

@@ -263,6 +286,8 @@ static int atana33xc20_probe(struct dp_aux_ep_device *aux_ep) return -ENOMEM; dev_set_drvdata(dev, panel);

+ panel->aux = aux_ep->aux; + panel->supply = devm_regulator_get(dev, "power"); if (IS_ERR(panel->supply)) return dev_err_probe(dev, PTR_ERR(panel->supply),

This implements the callback added by the patch ("drm/dp: Add wait_hpd_asserted() callback to struct drm_dp_aux").

With this change and all the two "DP AUX Endpoint" drivers changed to use wait_hpd_asserted(), we no longer need to have an long delay in the AUX transfer function. It's up to the panel code to make sure that the panel is powered now. If someone tried to call the aux transfer function without making sure the panel is powered we'll just get a normal transfer failure.

We'll still keep the wait for HPD in the pre_enable() function. Though it's probably not actually needed there, this driver is used in the old mode (pre-DP AUX Endpoints) and it may be important for those cases. If nothing else, it shouldn't cause any big problems.

NOTE: When handling the timeout for HPD we start the timer _after_ we've runtime resumed the device. This is definitely important for the panel on my homestar which comes up 170 ms after we start timing (the panel specifies 200 ms max). It's a little unclear how much of this extra time is due to some internal state machine in the parade firmware vs. debouncing but it seems to work for the two test cases I have to do it this way.

Signed-off-by: Douglas Anderson dianders@chromium.org Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org ---

Changes in v4: - Add comment that caller powered up the panel. - Mention in commit message debouncing vs. powering on timing.

Changes in v2: - Change is_hpd_asserted() to wait_hpd_asserted()

drivers/gpu/drm/bridge/parade-ps8640.c | 39 +++++++++++++++++--------- 1 file changed, 26 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c index ff4227f6d800..e880eee55822 100644 --- a/drivers/gpu/drm/bridge/parade-ps8640.c +++ b/drivers/gpu/drm/bridge/parade-ps8640.c @@ -168,23 +168,35 @@ static bool ps8640_of_panel_on_aux_bus(struct device *dev) return true; }

-static int ps8640_ensure_hpd(struct ps8640 *ps_bridge) +static int _ps8640_wait_hpd_asserted(struct ps8640 *ps_bridge, unsigned long wait_us) { struct regmap *map = ps_bridge->regmap[PAGE2_TOP_CNTL]; - struct device *dev = &ps_bridge->page[PAGE2_TOP_CNTL]->dev; int status; - int ret;

/* * Apparently something about the firmware in the chip signals that * HPD goes high by reporting GPIO9 as high (even though HPD isn't * actually connected to GPIO9). */ - ret = regmap_read_poll_timeout(map, PAGE2_GPIO_H, status, - status & PS_GPIO9, 20 * 1000, 200 * 1000); + return regmap_read_poll_timeout(map, PAGE2_GPIO_H, status, + status & PS_GPIO9, wait_us / 10, wait_us); +}

- if (ret < 0) - dev_warn(dev, "HPD didn't go high: %d\n", ret); +static int ps8640_wait_hpd_asserted(struct drm_dp_aux *aux, unsigned long wait_us) +{ + struct ps8640 *ps_bridge = aux_to_ps8640(aux); + struct device *dev = &ps_bridge->page[PAGE0_DP_CNTL]->dev; + int ret; + + /* + * Note that this function is called by code that has already powered + * the panel. We have to power ourselves up but we don't need to worry + * about powering the panel. + */ + pm_runtime_get_sync(dev); + ret = _ps8640_wait_hpd_asserted(ps_bridge, wait_us); + pm_runtime_mark_last_busy(dev); + pm_runtime_put_autosuspend(dev);

return ret; } @@ -323,9 +335,7 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux, int ret;

pm_runtime_get_sync(dev); - ret = ps8640_ensure_hpd(ps_bridge); - if (!ret) - ret = ps8640_aux_transfer_msg(aux, msg); + ret = ps8640_aux_transfer_msg(aux, msg); pm_runtime_mark_last_busy(dev); pm_runtime_put_autosuspend(dev);

@@ -369,8 +379,8 @@ static int __maybe_unused ps8640_resume(struct device *dev) * Mystery 200 ms delay for the "MCU to be ready". It's unclear if * this is truly necessary since the MCU will already signal that * things are "good to go" by signaling HPD on "gpio 9". See - * ps8640_ensure_hpd(). For now we'll keep this mystery delay just in - * case. + * _ps8640_wait_hpd_asserted(). For now we'll keep this mystery delay + * just in case. */ msleep(200);

@@ -406,7 +416,9 @@ static void ps8640_pre_enable(struct drm_bridge *bridge) int ret;

pm_runtime_get_sync(dev); - ps8640_ensure_hpd(ps_bridge); + ret = _ps8640_wait_hpd_asserted(ps_bridge, 200 * 1000); + if (ret < 0) + dev_warn(dev, "HPD didn't go high: %d\n", ret);

/* * The Manufacturer Command Set (MCS) is a device dependent interface @@ -682,6 +694,7 @@ static int ps8640_probe(struct i2c_client *client) ps_bridge->aux.name = "parade-ps8640-aux"; ps_bridge->aux.dev = dev; ps_bridge->aux.transfer = ps8640_aux_transfer; + ps_bridge->aux.wait_hpd_asserted = ps8640_wait_hpd_asserted; drm_dp_aux_init(&ps_bridge->aux);

pm_runtime_enable(dev);