[PATCH 07/12] drm/amd/display: Avoid Read Remote DPCD Many Times

[Roman.Li at amd.com]

From: Fangzhi Zuo <Jerry.Zuo at amd.com>

Reading remote dpcd is time consuming. Instead of reading each byte
one by one, read 16 bytes together.

Reviewed-by: ChiaHsuan (Tom) Chung <chiahsuan.chung at amd.com>
Signed-off-by: Fangzhi Zuo <Jerry.Zuo at amd.com>
Signed-off-by: Wayne Lin <Wayne.Lin at amd.com>
Signed-off-by: Roman Li <roman.li at amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c  | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 137f18d41f1b..32281bf62f70 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -1763,14 +1763,17 @@ static bool dp_get_link_current_set_bw(struct drm_dp_aux *aux, uint32_t *cur_lin
 	union lane_count_set lane_count;
 	u8 dp_link_encoding;
 	u8 link_bw_set = 0;
+	u8 data[16] = {0};
 
 	*cur_link_bw = 0;
 
-	if (drm_dp_dpcd_read(aux, DP_MAIN_LINK_CHANNEL_CODING_SET, &dp_link_encoding, 1) != 1 ||
-		drm_dp_dpcd_read(aux, DP_LANE_COUNT_SET, &lane_count.raw, 1) != 1 ||
-		drm_dp_dpcd_read(aux, DP_LINK_BW_SET, &link_bw_set, 1) != 1)
+	if (drm_dp_dpcd_read(aux, DP_LINK_BW_SET, data, 16) != 16)
 		return false;
 
+	dp_link_encoding = data[DP_MAIN_LINK_CHANNEL_CODING_SET - DP_LINK_BW_SET];
+	link_bw_set = data[DP_LINK_BW_SET - DP_LINK_BW_SET];
+	lane_count.raw = data[DP_LANE_COUNT_SET - DP_LINK_BW_SET];
+
 	switch (dp_link_encoding) {
 	case DP_8b_10b_ENCODING:
 		link_rate = link_bw_set;
-- 
2.34.1