[PATCH v3 3/4] drm/msm/dp: Prepare for link training per-segment for LTTPRs

Aleksandrs Vinarskis
2025-04-17T02:13:56Z

Per-segment link training requires knowing the number of LTTPRs
(if any) present. Store the count during LTTPRs' initialization.

Signed-off-by: Aleksandrs Vinarskis <alex.vinarskis@gmail.com>
---
drivers/gpu/drm/msm/dp/dp_display.c | 17 +++++++++++------
drivers/gpu/drm/msm/dp/dp_link.h | 1 +
2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 5c57c1d7ac60..ab8c1f19dcb4 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -367,16 +367,21 @@ 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, u8 *dpcd)
+static int msm_dp_display_lttpr_init(struct msm_dp_display_private *dp, u8 *dpcd)
{
- int rc;
+ int rc, lttpr_count;

if (drm_dp_read_lttpr_common_caps(dp->aux, dpcd, dp->link->lttpr_common_caps))
- return;
+ return 0;

- rc = drm_dp_lttpr_init(dp->aux, drm_dp_lttpr_count(dp->link->lttpr_common_caps));
- if (rc)
+ lttpr_count = drm_dp_lttpr_count(dp->link->lttpr_common_caps);
+ rc = drm_dp_lttpr_init(dp->aux, lttpr_count);
+ if (rc) {
DRM_ERROR("failed to set LTTPRs transparency mode, rc=%d\n", rc);
+ return 0;
+ }
+
+ return lttpr_count;
}

static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
@@ -390,7 +395,7 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
if (rc)
goto end;

- msm_dp_display_lttpr_init(dp, dpcd);
+ dp->link->lttpr_count = msm_dp_display_lttpr_init(dp, dpcd);

rc = msm_dp_panel_read_sink_caps(dp->panel, connector);
if (rc)
diff --git a/drivers/gpu/drm/msm/dp/dp_link.h b/drivers/gpu/drm/msm/dp/dp_link.h
index c47d75cfc720..ba47c6d19fbf 100644
--- a/drivers/gpu/drm/msm/dp/dp_link.h
+++ b/drivers/gpu/drm/msm/dp/dp_link.h
@@ -62,6 +62,7 @@ struct msm_dp_link_phy_params {

struct msm_dp_link {
u8 lttpr_common_caps[DP_LTTPR_COMMON_CAP_SIZE];
+ int lttpr_count;

u32 sink_request;
u32 test_response;
--
2.45.2