drm/amd/display: fix resume hang because of DP short pulse

There is a hard hang observed during resume from S3 when
the system receives a DP short pulse interrupt. This is
because there are two code paths contending for GPIO
access for AUX channel transactions. One such path is
through amdgpu_dm_display_resume() function which is
invoked from the regular system resume code path. The
other path is through handle_hpd_rx_irq(), which is
invoked in response to system receiving DP short pulse
interrupt. handle_hpd_rx_irq() guards against conflicting
GPIO access using hpd_lock, but the GPIO access from
amdgpu_dm_display_resume() remains unguarded.

This patch makes sure we use hpd_lock inside
amdgpu_dm_display_resume() to avoid race conditions
for GPIO access.

Signed-off-by: Arindam Nath <arindam.nath@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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 84995a48ec6110f722bcebe5917a624ec39e1b6c..74e32246ff309fb248487644df8c7d0ed72c9a3a 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -580,9 +580,11 @@ int amdgpu_dm_display_resume(struct amdgpu_device *adev )
                if (aconnector->mst_port)
                        continue;
 
+               mutex_lock(&aconnector->hpd_lock);
                dc_link_detect(aconnector->dc_link, false);
                aconnector->dc_sink = NULL;
                amdgpu_dm_update_connector_after_detect(aconnector);
+               mutex_unlock(&aconnector->hpd_lock);
        }
 
        /* Force mode set in atomic comit */