drm/msm/dp: Remove dead code related to downstream cap info

We read the downstream port count and capability info but never use it
anywhere. Remove 'ds_port_cnt' and 'ds_cap_info' and any associated code
from this driver. Fold the check for 'dfp_present' into a call to
drm_dp_is_branch() at the one place it is used to get rid of any member
storage related to downstream ports.

Cc: Vinod Polimera <quic_vpolimer@quicinc.com>
Cc: Kuogee Hsieh <quic_khsieh@quicinc.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/554984/
Link: https://lore.kernel.org/r/20230829184735.2841739-4-swboyd@chromium.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

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

@@ -43,9 +43,7 @@ static void dp_panel_read_psr_cap(struct dp_panel_private *panel)
 
 static int dp_panel_read_dpcd(struct dp_panel *dp_panel)
 {
-	int rc = 0;
-	size_t len;
-	ssize_t rlen;
+	int rc;
 	struct dp_panel_private *panel;
 	struct dp_link_info *link_info;
 	u8 *dpcd, major, minor;
@@ -79,25 +77,8 @@ static int dp_panel_read_dpcd(struct dp_panel *dp_panel)
 	if (drm_dp_enhanced_frame_cap(dpcd))
 		link_info->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;
 
-	dp_panel->dfp_present = dpcd[DP_DOWNSTREAMPORT_PRESENT];
-	dp_panel->dfp_present &= DP_DWN_STRM_PORT_PRESENT;
-
-	if (dp_panel->dfp_present && (dpcd[DP_DPCD_REV] > 0x10)) {
-		dp_panel->ds_port_cnt = dpcd[DP_DOWN_STREAM_PORT_COUNT];
-		dp_panel->ds_port_cnt &= DP_PORT_COUNT_MASK;
-		len = DP_DOWNSTREAM_PORTS * DP_DOWNSTREAM_CAP_SIZE;
-
-		rlen = drm_dp_dpcd_read(panel->aux,
-			DP_DOWNSTREAM_PORT_0, dp_panel->ds_cap_info, len);
-		if (rlen < len) {
-			DRM_ERROR("ds port status failed, rlen=%zd\n", rlen);
-			rc = -EINVAL;
-			goto end;
-		}
-	}
-
 	dp_panel_read_psr_cap(panel);
-end:
+
 	return rc;
 }
 
@@ -173,7 +154,7 @@ int dp_panel_read_sink_caps(struct dp_panel *dp_panel,
 		return -EINVAL;
 	}
 
-	if (dp_panel->dfp_present) {
+	if (drm_dp_is_branch(dp_panel->dpcd)) {
 		count = drm_dp_read_sink_count(panel->aux);
 		if (!count) {
 			DRM_ERROR("no downstream ports connected\n");

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

@@ -13,9 +13,6 @@
 
 struct edid;
 
-#define DP_DOWNSTREAM_PORTS		4
-#define DP_DOWNSTREAM_CAP_SIZE		4
-
 struct dp_display_mode {
 	struct drm_display_mode drm_mode;
 	u32 capabilities;
@@ -39,9 +36,6 @@ struct dp_panel_psr {
 struct dp_panel {
 	/* dpcd raw data */
 	u8 dpcd[DP_RECEIVER_CAP_SIZE];
-	u8 ds_cap_info[DP_DOWNSTREAM_PORTS * DP_DOWNSTREAM_CAP_SIZE];
-	u32 ds_port_cnt;
-	u32 dfp_present;
 
 	struct dp_link_info link_info;
 	struct drm_dp_desc desc;