Re: [PATCH] Revert "drm/msm/dp: Remove INIT_SETUP delay"

[Bjorn Andersson <andersson@kernel.org>]

On Mon, May 08, 2023 at 01:06:13AM +0000, Leonard Lausen wrote:
> This reverts commit e17af1c9d861dc177e5b56009bd4f71ace688d97.
> 
> Removing the delay of 100 units broke hot plug detection for USB-C displays on
> qcom sc7180 lazor devices. Lazor uses mdss for hot plug detection and declares
> dp_hot_plug_det in the dts. Other sc7180 based devices like aspire1 were not
> affected by the regression, as they do not rely on mdss and dp_hot_plug_det for
> hot plug detection.
> 
> Signed-off-by: Leonard Lausen <leonard@lausen.nl>
> Tested-by: Leonard Lausen <leonard@lausen.nl> # Trogdor (sc7180)
> Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> 
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index bde1a7ce442f..db9783ffd5cf 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1506,7 +1506,7 @@ void msm_dp_irq_postinstall(struct msm_dp *dp_display)
>         dp = container_of(dp_display, struct dp_display_private, dp_display);
>  
>         if (!dp_display->is_edp)
> -               dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 0);
> +               dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 100);

When booting with the cable connected on my X13s, 100 is long enough for
my display to time out and require me to disconnect and reconnect the
cable again.

Do we have any idea of why the reduction to 0 is causing an issue when
using the internal HPD?

Regards,
Bjorn

>  }
>  
>  bool msm_dp_wide_bus_available(const struct msm_dp *dp_display)
> -- 
> 2.30.2