drm/radeon: retry dcpd fetch

commit 0f28d1281b6c54cc98746ae61e44e7f540758ed4 upstream.

Retry the dpcd fetch several times.  Some eDP panels
fail several times before the fetch is successful.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=73530

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c
index 8d74de82456e880cb01d7e8132cf6c1caf5fa864..8b2c4c890507401d0d7f3d53ae46ec68658b70f5 100644 (file)
--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -412,19 +412,21 @@ bool radeon_dp_getdpcd(struct radeon_connector *radeon_connector)
 {
        struct radeon_connector_atom_dig *dig_connector = radeon_connector->con_priv;
        u8 msg[DP_DPCD_SIZE];
-       int ret;
+       int ret, i;
 
-       ret = drm_dp_dpcd_read(&radeon_connector->ddc_bus->aux, DP_DPCD_REV, msg,
-                              DP_DPCD_SIZE);
-       if (ret > 0) {
-               memcpy(dig_connector->dpcd, msg, DP_DPCD_SIZE);
+       for (i = 0; i < 7; i++) {
+               ret = drm_dp_dpcd_read(&radeon_connector->ddc_bus->aux, DP_DPCD_REV, msg,
+                                      DP_DPCD_SIZE);
+               if (ret == DP_DPCD_SIZE) {
+                       memcpy(dig_connector->dpcd, msg, DP_DPCD_SIZE);
 
-               DRM_DEBUG_KMS("DPCD: %*ph\n", (int)sizeof(dig_connector->dpcd),
-                             dig_connector->dpcd);
+                       DRM_DEBUG_KMS("DPCD: %*ph\n", (int)sizeof(dig_connector->dpcd),
+                                     dig_connector->dpcd);
 
-               radeon_dp_probe_oui(radeon_connector);
+                       radeon_dp_probe_oui(radeon_connector);
 
-               return true;
+                       return true;
+               }
        }
        dig_connector->dpcd[0] = 0;
        return false;