drm/amd/display: Avoid Read Remote DPCD Many Times

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@amd.com>
Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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 137f18d41f1b1129ffafc9c251f3c0118f105f55..32281bf62f706ce8b4db7b7203bf819de703e297 100644 (file)
--- 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;