Re: [PATCH v5 6/8] drm/msm: dp: handle the IRQ_HPD events reported by USB-C

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] drm/msm/dp: missing display initialization on coalesced plug and IRQ_HPD events
--

commit de969f3016008fcb55e0b380cb8e0c733c719543
Author: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

drm/msm: dp: handle the IRQ_HPD events reported by USB-C

This commit allows the MSM DisplayPort driver to handle IRQ_HPD events
delivered over OOB events (like USB-C AltMode).

> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1559,11 +1559,12 @@ void msm_dp_bridge_hpd_notify(struct drm_bridge *bridge,
[ ... ]
>  	if (status == connector_status_connected) {
> -		if (hpd_link_status == ISR_HPD_REPLUG_COUNT) {
> +		if (hpd_link_status == ISR_IRQ_HPD_PULSE_COUNT ||
> +		    event == DRM_CONNECTOR_DP_IRQ_HPD) {
> +			msm_dp_irq_hpd_handle(dp);
> +		} else if (hpd_link_status == ISR_HPD_REPLUG_COUNT) {
>  			msm_dp_hpd_unplug_handle(dp);
>  			msm_dp_hpd_plug_handle(dp);
> -		} else if (hpd_link_status == ISR_IRQ_HPD_PULSE_COUNT) {
> -			msm_dp_irq_hpd_handle(dp);
>  		} else {
>  			msm_dp_hpd_plug_handle(dp);
>  		}

[Severity: High]
Does this code handle coalesced connection and IRQ_HPD events correctly?

If the USB Type-C AltMode driver coalesces an initial connection and a pending
IRQ_HPD event into a single notification, msm_dp_bridge_hpd_notify() receives
both status == connector_status_connected and event ==
DRM_CONNECTOR_DP_IRQ_HPD.

The mutual exclusion block in drivers/gpu/drm/msm/dp/dp_display.c prioritizes
event == DRM_CONNECTOR_DP_IRQ_HPD, branching to msm_dp_irq_hpd_handle() and
entirely skipping msm_dp_hpd_plug_handle().

Because msm_dp_hpd_plug_handle() is skipped, dp->plugged remains false,
the DP PHY is not initialized, and AUX transfers remain disabled. The
subsequent msm_dp_irq_hpd_handle() then attempts an AUX read which immediately
fails with -ENXIO, abandoning the initialization and leaving the display
blank.

Is it possible to ensure msm_dp_hpd_plug_handle() is still called when a new
connection occurs alongside an IRQ_HPD event?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260920-hpd-irq-events-v5-0-ff1de0090c72@oss.qualcomm.com?part=6

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