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

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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>
This commit is contained in:
Fangzhi Zuo
2025-07-09 21:42:54 -04:00
committed by Alex Deucher
parent 6ec8a5cbec
commit fa5f99ee72
1 changed files with 6 additions and 3 deletions
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9
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
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@@ -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;