drm/amd/display: Add HBlank reduction DPCD write to DPMS sequence

[Why]
Certain small HBlank timings may not have a large enough HBlank to
support audio when low bpp DSC is enabled. HBlank expansion by the
source can solve this problem, but requires the branch/sink to support
HBlank reduction.

[How]
Update DPMS sequence to call DM to perform DPCD write to enable HBlank
reduction on the branch/sink. Add stub in dm_helpers to be implemented
later.

Reviewed-by: Michael Strauss <michael.strauss@amd.com>
Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: George Shen <george.shen@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>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index 6cbbb71d752b..fbd80d8545a8 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -885,6 +885,12 @@ bool dm_helpers_dp_write_dsc_enable(
 	return ret;
 }
 
+bool dm_helpers_dp_write_hblank_reduction(struct dc_context *ctx, const struct dc_stream_state *stream)
+{
+	// TODO
+	return false;
+}
+
 bool dm_helpers_is_dp_sink_present(struct dc_link *link)
 {
 	bool dp_sink_present;