disp: msm: dp: avoid duplicate read of link status

During link training, after the swing/preemphasis is updated, the driver
is supposed to poll the link status on the sink and quit once the
LINK_STATUS_UPDATED bit is set and also latch the next set of
swing/preemphasis requested by the sink. But currently, the driver is
exiting the loop only when the LINK_STATUS_UPDATED bit is cleared. So,
it also latches the swing/emphasis request from the second read.

Typically, the SW read is slow enough that the bit is set on the first
read. The driver then reads the second time and exits the loop, since
the bit would be cleared then. In most cases, this doesn't affect
the training sequence, since the swing/preemphasis request for next
attempt is retained on the second read. But, atleast in one
specific case, it was observed that the swing/emphasis request
gets reset along with LINK_STATUS_UPDATED and so the driver ends
up missing the actual request and latches incorrect values instead.
This causes link training to fail as it keep retrying with the
same values that it starts with.

This change fixes the exit condition check so the driver quits the loop
as soon as the LINK_STATUS_UPDATED bit is set.

Change-Id: I7f5d9c6b30d48e113aef628d2ab2c1bd972fe743
Signed-off-by: Rajkumar Subbiah <quic_rsubbia@quicinc.com>

msm/dp/dp_ctrl.c

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * Copyright (c) 2021, Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) 2022, Qualcomm Innovation Center, Inc. All rights reserved.
  * Copyright (c) 2012-2021, The Linux Foundation. All rights reserved.
  */
 
@@ -278,7 +278,7 @@ static int dp_ctrl_read_link_status(struct dp_ctrl_private *ctrl,
 			break;
 		}
 
-		if (!(link_status[offset] & DP_LINK_STATUS_UPDATED))
+		if (link_status[offset] & DP_LINK_STATUS_UPDATED)
 			break;
 	}