drm/msm/dp: do not reinitialize phy unless retry during link training

DP PHY re-initialization done using dp_ctrl_reinitialize_mainlink() will
cause PLL unlocked initially and then PLL gets locked at the end of
initialization. PLL_UNLOCKED interrupt will fire during this time if the
interrupt mask is enabled.

However currently DP driver link training implementation incorrectly
re-initializes PHY unconditionally during link training as the PHY was
already configured in dp_ctrl_enable_mainlink_clocks().

Fix this by re-initializing the PHY only if the previous link training
failed.

[drm:dp_aux_isr] *ERROR* Unexpected DP AUX IRQ 0x01000000 when not busy

Fixes: c943b49 ("drm/msm/dp: add displayPort driver support")
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/30
Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Tested-by: Abhinav Kumar <quic_abhinavk@quicinc.com> # sc7280
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/551847/
Link: https://lore.kernel.org/r/1691533190-19335-1-git-send-email-quic_khsieh@quicinc.com
[quic_abhinavk@quicinc.com: added line break in commit text]
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

Author: Kuogee Hsieh

drivers/gpu/drm/msm/dp/dp_ctrl.c

@@ -1774,13 +1774,6 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
 		return rc;
 
 	while (--link_train_max_retries) {
-		rc = dp_ctrl_reinitialize_mainlink(ctrl);
-		if (rc) {
-			DRM_ERROR("Failed to reinitialize mainlink. rc=%d\n",
-					rc);
-			break;
-		}
-
 		training_step = DP_TRAINING_NONE;
 		rc = dp_ctrl_setup_main_link(ctrl, &training_step);
 		if (rc == 0) {
@@ -1832,6 +1825,12 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
 			/* stop link training before start re training  */
 			dp_ctrl_clear_training_pattern(ctrl);
 		}
+
+		rc = dp_ctrl_reinitialize_mainlink(ctrl);
+		if (rc) {
+			DRM_ERROR("Failed to reinitialize mainlink. rc=%d\n", rc);
+			break;
+		}
 	}
 
 	if (ctrl->link->sink_request & DP_TEST_LINK_PHY_TEST_PATTERN)