linux-kernel - [PATCH AUTOSEL 5.4 20/23] drm/amd/display: Retry AUX write when fail occurs

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Date:   Mon, 31 Aug 2020 11:30:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Wayne Lin <Wayne.Lin@....com>, Hersen Wu <hersenxs.wu@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.4 20/23] drm/amd/display: Retry AUX write when fail occurs

From: Wayne Lin <Wayne.Lin@....com>

[ Upstream commit ef67d792a2fc578319399f605fbec2f99ecc06ea ]

[Why]
In dm_dp_aux_transfer() now, we forget to handle AUX_WR fail cases. We
suppose every write wil get done successfully and hence some AUX
commands might not sent out indeed.

[How]
Check if AUX_WR success. If not, retry it.

Signed-off-by: Wayne Lin <Wayne.Lin@....com>
Reviewed-by: Hersen Wu <hersenxs.wu@....com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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 28a6c7b2ef4bb..2f858507ca702 100644
--- 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
@@ -101,7 +101,7 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
 	result = dc_link_aux_transfer_raw(TO_DM_AUX(aux)->ddc_service, &payload,
 				      &operation_result);
 
-	if (payload.write)
+	if (payload.write && result >= 0)
 		result = msg->size;
 
 	if (result < 0)
-- 
2.25.1