From: Nicholas Kazlauskas nicholas.kazlauskas@amd.com

[Why] If the "max bpc" isn't explicitly set in the atomic state then it have a value of 0. This has the correct behavior of limiting a panel to 8bpc in the case where the panel supports 8bpc. In the case of eDP panels this isn't a true assumption - there are panels that can only do 6bpc.

Banding occurs for these displays.

[How] Initialize the max_bpc when the connector resets to 8bpc. Also carry over the value when the state is duplicated.

Bugzilla: https://bugs.freedesktop.org/108825 Fixes: 307638884f72 ("drm/amd/display: Support amdgpu "max bpc" connector property")

Backport of commit 49f1c44b581b08e3289127ffe58bd208c3166701 upstream.

Fixes regression caused by the automatic patch select of these two patches: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/driv... https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/driv... Bug: https://bugs.freedesktop.org/show_bug.cgi?id=109122

Cc: Sasha Levin sashal@kernel.org Signed-off-by: Nicholas Kazlauskas nicholas.kazlauskas@amd.com Reviewed-by: Alex Deucher alexander.deucher@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com (cherry picked from commit 49f1c44b581b08e3289127ffe58bd208c3166701) Cc: stable@vger.kernel.org # 4.19.x --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index 299def84e69c..d792735f1365 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -2894,6 +2894,7 @@ void amdgpu_dm_connector_funcs_reset(struct drm_connector *connector) state->underscan_enable = false; state->underscan_hborder = 0; state->underscan_vborder = 0; + state->max_bpc = 8;

__drm_atomic_helper_connector_reset(connector, &state->base); } @@ -2911,6 +2912,7 @@ amdgpu_dm_connector_atomic_duplicate_state(struct drm_connector *connector) if (new_state) { __drm_atomic_helper_connector_duplicate_state(connector, &new_state->base); + new_state->max_bpc = state->max_bpc; return &new_state->base; }