drm/amd/display: Move sleep into each retry for retrieve_link_cap()

[Why]
When a monitor is booting it's possible that it isn't ready to retrieve
link caps and this can lead to an EDID read failure:

```
[drm:retrieve_link_cap [amdgpu]] *ERROR* retrieve_link_cap: Read receiver caps dpcd data failed.
amdgpu 0000:c5:00.0: [drm] *ERROR* No EDID read.
```

[How]
Rather than msleep once and try a few times, msleep each time.  Should
be no changes for existing working monitors, but should correct reading
caps on a monitor that is slow to boot.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4672
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 669dca37b3348a447db04bbdcbb3def94d5997cc)
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
index b12c11bd6a1498777959896c1dc8e5ea8e2453c7..4d0079b44de12812eac102f980511c54bc9dc23a 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
+++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
@@ -1734,12 +1734,13 @@ static bool retrieve_link_cap(struct dc_link *link)
        }
 
        dpcd_set_source_specific_data(link);
-       /* Sink may need to configure internals based on vendor, so allow some
-        * time before proceeding with possibly vendor specific transactions
-        */
-       msleep(post_oui_delay);
 
        for (i = 0; i < read_dpcd_retry_cnt; i++) {
+               /*
+                * Sink may need to configure internals based on vendor, so allow some
+                * time before proceeding with possibly vendor specific transactions
+                */
+               msleep(post_oui_delay);
                status = core_link_read_dpcd(
                                link,
                                DP_DPCD_REV,