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SubjectRe: [PATCH v3 4/4] drm/bridge: parade-ps8640: Provide wait_hpd_asserted() in struct drm_dp_aux
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On 18/04/2022 20:17, Douglas Anderson wrote:
> 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.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Minor nit below

> ---
>
> (no changes since v2)
>
> Changes in v2:
> - Change is_hpd_asserted() to wait_hpd_asserted()
>
> drivers/gpu/drm/bridge/parade-ps8640.c | 34 ++++++++++++++++----------
> 1 file changed, 21 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> index 9766cbbd62ad..2f19a8c89880 100644
> --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> @@ -168,23 +168,30 @@ 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;
> +
> + 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);

I'd add a note here, that the called should have already woken up the
device.

>
> return ret;
> }
> @@ -323,9 +330,7 @@ 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 +374,8 @@ 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 +411,9 @@ 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
> @@ -652,6 +659,7 @@ 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);


--
With best wishes
Dmitry

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