Re: [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.barysh...@oss.qualcomm.com>
Signed-off-by: Aleksandrs Vinarskis <alex.vinars...@gmail.com>
Tested-by: Johan Hovold <johan+lin...@kernel.org>
Tested-by: Rob Clark <robdcl...@gmail.com>

Hi Aleksandrs,

For this patch and the rest of the series:

Tested-by: Jessica Zhang <quic_jessz...@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);