[PATCH v4 1/4] drm/msm/dp: Fix support of LTTPR initialization

[Jessica Zhang]

On 4/29/2025 5:09 PM, Aleksandrs Vinarskis wrote:
> Initialize LTTPR before msm_dp_panel_read_sink_caps, as DPTX shall
> (re)read DPRX caps after LTTPR detection, as required by DP 2.1,
> Section 3.6.7.6.1.
> 
> Fixes: 72d0af4accd9 ("drm/msm/dp: Add support for LTTPR handling")
> 
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov at oss.qualcomm.com>
> Signed-off-by: Aleksandrs Vinarskis <alex.vinarskis at gmail.com>
> Tested-by: Johan Hovold <johan+linaro at kernel.org>
> Tested-by: Rob Clark <robdclark at gmail.com>

Hi Aleksandrs,

For this patch and the rest of the series:

Tested-by: Jessica Zhang <quic_jesszhan at quicinc.com> # SA8775P

Thanks,

Jessica Zhang

> ---
>   drivers/gpu/drm/msm/dp/dp_display.c | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index bbc47d86ae9e..fc07cce68382 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -367,12 +367,12 @@ static int msm_dp_display_send_hpd_notification(struct msm_dp_display_private *d
>   	return 0;
>   }
>   
> -static void msm_dp_display_lttpr_init(struct msm_dp_display_private *dp)
> +static void msm_dp_display_lttpr_init(struct msm_dp_display_private *dp, u8 *dpcd)
>   {
>   	u8 lttpr_caps[DP_LTTPR_COMMON_CAP_SIZE];
>   	int rc;
>   
> -	if (drm_dp_read_lttpr_common_caps(dp->aux, dp->panel->dpcd, lttpr_caps))
> +	if (drm_dp_read_lttpr_common_caps(dp->aux, dpcd, lttpr_caps))
>   		return;
>   
>   	rc = drm_dp_lttpr_init(dp->aux, drm_dp_lttpr_count(lttpr_caps));
> @@ -385,12 +385,17 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
>   	struct drm_connector *connector = dp->msm_dp_display.connector;
>   	const struct drm_display_info *info = &connector->display_info;
>   	int rc = 0;
> +	u8 dpcd[DP_RECEIVER_CAP_SIZE];
>   
> -	rc = msm_dp_panel_read_sink_caps(dp->panel, connector);
> +	rc = drm_dp_read_dpcd_caps(dp->aux, dpcd);
>   	if (rc)
>   		goto end;
>   
> -	msm_dp_display_lttpr_init(dp);
> +	msm_dp_display_lttpr_init(dp, dpcd);
> +
> +	rc = msm_dp_panel_read_sink_caps(dp->panel, connector);
> +	if (rc)
> +		goto end;
>   
>   	msm_dp_link_process_request(dp->link);
>