drm/msm/dp: Account for LTTPRs capabilities

Take into account LTTPR capabilities when selecting maximum allowed
link rate, number of data lines.

Fixes: 72d0af4 ("drm/msm/dp: Add support for LTTPR handling")
Reviewed-by: Abel Vesa <[email protected]>
Reviewed-by: Abhinav Kumar <[email protected]>
Reviewed-by: Dmitry Baryshkov <[email protected]>
Signed-off-by: Aleksandrs Vinarskis <[email protected]>
Tested-by: Jessica Zhang <[email protected]> # SA8775P
Tested-by: Johan Hovold <[email protected]>
Tested-by: Rob Clark <[email protected]>
Patchwork: https://patchwork.freedesktop.org/patch/652302/
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Dmitry Baryshkov <[email protected]>

Author: alexVinarskis

drivers/gpu/drm/msm/dp/dp_display.c

@@ -362,13 +362,12 @@ static int msm_dp_display_send_hpd_notification(struct msm_dp_display_private *d
 
 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, dpcd, lttpr_caps))
+	if (drm_dp_read_lttpr_common_caps(dp->aux, dpcd, dp->link->lttpr_common_caps))
 		return;
 
-	rc = drm_dp_lttpr_init(dp->aux, drm_dp_lttpr_count(lttpr_caps));
+	rc = drm_dp_lttpr_init(dp->aux, drm_dp_lttpr_count(dp->link->lttpr_common_caps));
 	if (rc)
 		DRM_ERROR("failed to set LTTPRs transparency mode, rc=%d\n", rc);
 }

drivers/gpu/drm/msm/dp/dp_link.h

@@ -7,6 +7,7 @@
 #define _DP_LINK_H_
 
 #include "dp_aux.h"
+#include <drm/display/drm_dp_helper.h>
 
 #define DS_PORT_STATUS_CHANGED 0x200
 #define DP_TEST_BIT_DEPTH_UNKNOWN 0xFFFFFFFF
@@ -60,6 +61,8 @@ struct msm_dp_link_phy_params {
 };
 
 struct msm_dp_link {
+	u8 lttpr_common_caps[DP_LTTPR_COMMON_CAP_SIZE];
+
 	u32 sink_request;
 	u32 test_response;
 

drivers/gpu/drm/msm/dp/dp_panel.c

@@ -47,7 +47,7 @@ static void msm_dp_panel_read_psr_cap(struct msm_dp_panel_private *panel)
 
 static int msm_dp_panel_read_dpcd(struct msm_dp_panel *msm_dp_panel)
 {
-	int rc;
+	int rc, max_lttpr_lanes, max_lttpr_rate;
 	struct msm_dp_panel_private *panel;
 	struct msm_dp_link_info *link_info;
 	u8 *dpcd, major, minor;
@@ -75,6 +75,16 @@ static int msm_dp_panel_read_dpcd(struct msm_dp_panel *msm_dp_panel)
 	if (link_info->rate > msm_dp_panel->max_dp_link_rate)
 		link_info->rate = msm_dp_panel->max_dp_link_rate;
 
+	/* Limit data lanes from LTTPR capabilities, if any */
+	max_lttpr_lanes = drm_dp_lttpr_max_lane_count(panel->link->lttpr_common_caps);
+	if (max_lttpr_lanes && max_lttpr_lanes < link_info->num_lanes)
+		link_info->num_lanes = max_lttpr_lanes;
+
+	/* Limit link rate from LTTPR capabilities, if any */
+	max_lttpr_rate = drm_dp_lttpr_max_link_rate(panel->link->lttpr_common_caps);
+	if (max_lttpr_rate && max_lttpr_rate < link_info->rate)
+		link_info->rate = max_lttpr_rate;
+
 	drm_dbg_dp(panel->drm_dev, "version: %d.%d\n", major, minor);
 	drm_dbg_dp(panel->drm_dev, "link_rate=%d\n", link_info->rate);
 	drm_dbg_dp(panel->drm_dev, "lane_count=%d\n", link_info->num_lanes);