drm/i915: Dont -ETIMEDOUT on identical new and previous (count, crc).

By Vesa DP 1.2 spec TEST_CRC_COUNT is a "4 bit wrap counter which
increments each time the TEST_CRC_x_x are updated."

However if we are trying to verify the screen hasn't changed we get
same (count, crc) pair twice. Without this patch we would return
-ETIMEOUT in this case.

So, if in 6 vblanks the pair (count, crc) hasn't changed we
return it anyway instead of returning error and let test case decide
if it was right or not.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rafael Antognolli <rafael.antognolli@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index abcc2a3..54e9b53 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4065,6 +4065,7 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
        u8 buf;
        int count, ret;
        int attempts = 6;
+       bool old_equal_new;
 
        ret = intel_dp_sink_crc_start(intel_dp);
        if (ret)
@@ -4079,6 +4080,7 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
                        goto stop;
                }
                count = buf & DP_TEST_COUNT_MASK;
+
                /*
                 * Count might be reset during the loop. In this case
                 * last known count needs to be reset as well.
@@ -4090,17 +4092,24 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
                        ret = -EIO;
                        goto stop;
                }
-       } while (--attempts && (count == 0 || (count == intel_dp->sink_crc.last_count &&
-                                              !memcmp(intel_dp->sink_crc.last_crc, crc,
-                                                      6 * sizeof(u8)))));
+
+               old_equal_new = (count == intel_dp->sink_crc.last_count &&
+                                !memcmp(intel_dp->sink_crc.last_crc, crc,
+                                        6 * sizeof(u8)));
+
+       } while (--attempts && (count == 0 || old_equal_new));
 
        intel_dp->sink_crc.last_count = buf & DP_TEST_COUNT_MASK;
        memcpy(intel_dp->sink_crc.last_crc, crc, 6 * sizeof(u8));
 
        if (attempts == 0) {
-               DRM_DEBUG_KMS("Panel is unable to calculate CRC after 6 vblanks\n");
-               ret = -ETIMEDOUT;
-               goto stop;
+               if (old_equal_new) {
+                       DRM_DEBUG_KMS("Unreliable Sink CRC counter: Current returned CRC is identical to the previous one\n");
+               } else {
+                       DRM_ERROR("Panel is unable to calculate any CRC after 6 vblanks\n");
+                       ret = -ETIMEDOUT;
+                       goto stop;
+               }
        }
 
 stop: