The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3b2e973dff59d88bee1d814ddf8762a24fc02b60 Mon Sep 17 00:00:00 2001

From: Aaron Ma aaron.ma@canonical.com Date: Wed, 8 Jul 2020 04:16:22 -0400 Subject: [PATCH] drm/amd/display: add dmcub check on RENOIR

RENOIR loads dmub fw not dmcu, check dmcu only will prevent loading iram, it breaks backlight control.

Bug: https://bugzilla.kernel.org/show_bug.cgi?id=208277 Acked-by: Alex Deucher alexander.deucher@amd.com Reviewed-by: Nicholas Kazlauskas nicholas.kazlauskas@amd.com Signed-off-by: Aaron Ma aaron.ma@canonical.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Cc: stable@vger.kernel.org

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 10ac8076d4f2..db5e0bb0d935 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -1358,7 +1358,7 @@ static int dm_late_init(void *handle) struct dmcu *dmcu = NULL; bool ret;

- if (!adev->dm.fw_dmcu) + if (!adev->dm.fw_dmcu && !adev->dm.dmub_fw) return detect_mst_link_for_all_connectors(adev->ddev);

dmcu = adev->dm.dc->res_pool->dmcu;