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SubjectRe: [RFC PATCH 4/6] drm/panel-edp: Take advantage of is_hpd_asserted() in struct drm_dp_aux
From
On 09/04/2022 05:36, Douglas Anderson wrote:
> Let's add support for being able to read the HPD pin even if it's
> hooked directly to the controller. This will allow us to get more
> accurate delays also lets us take away the waiting in the AUX transfer
> functions of the eDP controller drivers.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
> drivers/gpu/drm/panel/panel-edp.c | 37 ++++++++++++++++++++++++++-----
> 1 file changed, 31 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
> index 1732b4f56e38..4a143eb9544b 100644
> --- a/drivers/gpu/drm/panel/panel-edp.c
> +++ b/drivers/gpu/drm/panel/panel-edp.c
> @@ -417,6 +417,19 @@ static int panel_edp_get_hpd_gpio(struct device *dev, struct panel_edp *p)
> return 0;
> }
>
> +static bool panel_edp_can_read_hpd(struct panel_edp *p)
> +{
> + return !p->no_hpd && (p->hpd_gpio || (p->aux && p->aux->is_hpd_asserted));
> +}
> +
> +static bool panel_edp_read_hpd(struct panel_edp *p)
> +{
> + if (p->hpd_gpio)
> + return gpiod_get_value_cansleep(p->hpd_gpio);
> +
> + return p->aux->is_hpd_asserted(p->aux);
> +}
> +
> static int panel_edp_prepare_once(struct panel_edp *p)
> {
> struct device *dev = p->base.dev;
> @@ -441,13 +454,21 @@ static int panel_edp_prepare_once(struct panel_edp *p)
> if (delay)
> msleep(delay);
>
> - if (p->hpd_gpio) {
> + if (panel_edp_can_read_hpd(p)) {
> if (p->desc->delay.hpd_absent)
> hpd_wait_us = p->desc->delay.hpd_absent * 1000UL;
> else
> hpd_wait_us = 2000000;
>
> - err = readx_poll_timeout(gpiod_get_value_cansleep, p->hpd_gpio,
> + /*
> + * Extra max delay, mostly to account for ps8640. ps8640
> + * is crazy and the bridge chip driver itself has over 200 ms
> + * of delay if it needs to do the pm_runtime resume of the
> + * bridge chip to read the HPD.
> + */
> + hpd_wait_us += 3000000;

I think this should come in a separate commit and ideally this should be
configurable somehow. Other hosts wouldn't need such 'additional' delay.

With this change removed:

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


> +
> + err = readx_poll_timeout(panel_edp_read_hpd, p,
> hpd_asserted, hpd_asserted,
> 1000, hpd_wait_us);
> if (hpd_asserted < 0)
> @@ -532,18 +553,22 @@ static int panel_edp_enable(struct drm_panel *panel)
> /*
> * If there is a "prepare_to_enable" delay then that's supposed to be
> * the delay from HPD going high until we can turn the backlight on.
> - * However, we can only count this if HPD is handled by the panel
> - * driver, not if it goes to a dedicated pin on the controller.
> + * However, we can only count this if HPD is readable by the panel
> + * driver.
> + *
> * If we aren't handling the HPD pin ourselves then the best we
> * can do is assume that HPD went high immediately before we were
> - * called (and link training took zero time).
> + * called (and link training took zero time). Note that "no-hpd"
> + * actually counts as handling HPD ourselves since we're doing the
> + * worst case delay (in prepare) ourselves.
> *
> * NOTE: if we ever end up in this "if" statement then we're
> * guaranteed that the panel_edp_wait() call below will do no delay.
> * It already handles that case, though, so we don't need any special
> * code for it.
> */
> - if (p->desc->delay.prepare_to_enable && !p->hpd_gpio && !p->no_hpd)
> + if (p->desc->delay.prepare_to_enable &&
> + !panel_edp_can_read_hpd(p) && !p->no_hpd)
> delay = max(delay, p->desc->delay.prepare_to_enable);
>
> if (delay)


--
With best wishes
Dmitry

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