In some cases like when PSR just got enabled the panel need more vblank
times to calculate CRC. I figured that out with the new PSR test cases
facing some cases that I had a green screen but a blank CRC. Even with
2 vblank waits on kernel + 2 vblank waits on test case.

So let's give up to 6 vblank wait time. However we now check for
TEST_CRC_COUNT that shows when panel finished to calculate CRC and
has it ready.

Signed-off-by: Rodrigo Vivi <rodrigo.v...@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 20 ++++++++++++++------
 include/drm/drm_dp_helper.h     |  5 +++--
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index f79473b..eda6467 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3468,21 +3468,29 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 
*crc)
        struct drm_device *dev = intel_dig_port->base.base.dev;
        struct intel_crtc *intel_crtc =
                to_intel_crtc(intel_dig_port->base.base.crtc);
-       u8 buf[1];
+       u8 buf;
+       int test_crc_count;
+       int attempts = 6;
 
-       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK_MISC, buf) < 0)
+       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK_MISC, &buf) < 0)
                return -EAGAIN;
 
-       if (!(buf[0] & DP_TEST_CRC_SUPPORTED))
+       if (!(buf & DP_TEST_CRC_SUPPORTED))
                return -ENOTTY;
 
+       test_crc_count = buf & DP_TEST_COUNT_MASK;
+
        if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_TEST_SINK,
                               DP_TEST_SINK_START) < 0)
                return -EAGAIN;
 
-       /* Wait 2 vblanks to be sure we will have the correct CRC value */
-       intel_wait_for_vblank(dev, intel_crtc->pipe);
-       intel_wait_for_vblank(dev, intel_crtc->pipe);
+       do {
+               drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK_MISC, &buf);
+               intel_wait_for_vblank(dev, intel_crtc->pipe);
+       } while(attempts-- && (buf & DP_TEST_COUNT_MASK) <= test_crc_count);
+
+       if (attempts == 0)
+               return -EAGAIN;
 
        if (drm_dp_dpcd_read(&intel_dp->aux, DP_TEST_CRC_R_CR, crc, 6) < 0)
                return -EAGAIN;
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 9305c71..8edeed0 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -303,7 +303,8 @@
 #define DP_TEST_CRC_B_CB                   0x244
 
 #define DP_TEST_SINK_MISC                  0x246
-#define DP_TEST_CRC_SUPPORTED              (1 << 5)
+# define DP_TEST_CRC_SUPPORTED             (1 << 5)
+# define DP_TEST_COUNT_MASK                0x7
 
 #define DP_TEST_RESPONSE                   0x260
 # define DP_TEST_ACK                       (1 << 0)
@@ -313,7 +314,7 @@
 #define DP_TEST_EDID_CHECKSUM              0x261
 
 #define DP_TEST_SINK                       0x270
-#define DP_TEST_SINK_START         (1 << 0)
+# define DP_TEST_SINK_START                (1 << 0)
 
 #define DP_PAYLOAD_TABLE_UPDATE_STATUS      0x2c0   /* 1.2 MST */
 # define DP_PAYLOAD_TABLE_UPDATED           (1 << 0)
-- 
1.9.3

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