During initalization of the DisplayPort controller an EV_HPD_INIT_SETUP
event is generated, but with a delay of 100 units. This delay existed to
circumvent bug in the QMP combo PHY driver, where if the DP part was
powered up before USB, the common properties would not be properly
initialized - and USB wouldn't work.

This issue was resolved in the recent refactoring of the QMP driver,
so it's now possible to remove this delay.

While there is still a timing dependency in the current implementation,
test indicates that it's now possible to boot with an external display
on USB Type-C and have the display power up, without disconnecting and
reconnecting the cable.

Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
---
 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 db9783ffd5cf..bde1a7ce442f 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, 100);
+		dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 0);
 }
 
 bool msm_dp_wide_bus_available(const struct msm_dp *dp_display)
-- 
2.37.3

On Tue, 17 Jan 2023 09:29:51 -0800, Bjorn Andersson wrote:
> During initalization of the DisplayPort controller an EV_HPD_INIT_SETUP
> event is generated, but with a delay of 100 units. This delay existed to
> circumvent bug in the QMP combo PHY driver, where if the DP part was
> powered up before USB, the common properties would not be properly
> initialized - and USB wouldn't work.
> 
> This issue was resolved in the recent refactoring of the QMP driver,
> so it's now possible to remove this delay.
> 
> [...]

Applied, thanks!

[1/1] drm/msm/dp: Remove INIT_SETUP delay
      https://gitlab.freedesktop.org/lumag/msm/-/commit/e17af1c9d861

Best regards,
-- 
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

On 1/17/2023 9:29 AM, Bjorn Andersson wrote:
> During initalization of the DisplayPort controller an EV_HPD_INIT_SETUP
> event is generated, but with a delay of 100 units. This delay existed to
> circumvent bug in the QMP combo PHY driver, where if the DP part was
> powered up before USB, the common properties would not be properly
> initialized - and USB wouldn't work.
>
> This issue was resolved in the recent refactoring of the QMP driver,
> so it's now possible to remove this delay.
>
> While there is still a timing dependency in the current implementation,
> test indicates that it's now possible to boot with an external display
> on USB Type-C and have the display power up, without disconnecting and
> reconnecting the cable.
>
> Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
> ---
>   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 db9783ffd5cf..bde1a7ce442f 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, 100);
> +		dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 0);
>   }
>   
>   bool msm_dp_wide_bus_available(const struct msm_dp *dp_display)