drm/bridge: analogix_dp: Don't use fast link training when panel just powered up

Panel would reset its setting when it powers down. It would forget the last
succeeded link training setting. So we can't use the last successful link
training setting to do fast link training. Let's reset fast_train_enable in
analogix_dp_bridge_disable();

Cc: Stéphane Marchesin <marcheu@chromium.org>
Signed-off-by: Nzain wang <wzz@rock-chips.com>
Signed-off-by: NSean Paul <seanpaul@chromium.org>
Signed-off-by: NThierry Escande <thierry.escande@collabora.com>
Signed-off-by: NEnric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: NArchit Taneja <architt@codeaurora.org>
Signed-off-by: NAndrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180423105003.9004-4-enric.balletbo@collabora.com

drivers/gpu/drm/bridge/analogix/analogix_dp_core.c

@@ -579,14 +579,14 @@ static int analogix_dp_process_equalizer_training(struct analogix_dp_device *dp)
 		if (retval != 1) {
 			dev_err(dp->dev, "failed to read downspread %d\n",
 				retval);
-			dp->fast_train_support = false;
+			dp->fast_train_enable = false;
 		} else {
-			dp->fast_train_support =
+			dp->fast_train_enable =
 				(spread & DP_NO_AUX_HANDSHAKE_LINK_TRAINING) ?
 					true : false;
 		}
 		dev_dbg(dp->dev, "fast link training %s\n",
-			dp->fast_train_support ? "supported" : "unsupported");
+			dp->fast_train_enable ? "supported" : "unsupported");
 
 		/* set enhanced mode if available */
 		analogix_dp_set_enhanced_mode(dp);
@@ -793,7 +793,7 @@ static int analogix_dp_fast_link_train(struct analogix_dp_device *dp)
 
 static int analogix_dp_train_link(struct analogix_dp_device *dp)
 {
-	if (dp->fast_train_support)
+	if (dp->fast_train_enable)
 		return analogix_dp_fast_link_train(dp);
 
 	return analogix_dp_full_link_train(dp, dp->video_info.max_lane_count,
@@ -1197,6 +1197,7 @@ static void analogix_dp_bridge_disable(struct drm_bridge *bridge)
 		DRM_ERROR("failed to setup the panel ret = %d\n", ret);
 
 	dp->psr_enable = false;
+	dp->fast_train_enable = false;
 	dp->dpms_mode = DRM_MODE_DPMS_OFF;
 }
 

drivers/gpu/drm/bridge/analogix/analogix_dp_core.h

@@ -173,7 +173,7 @@ struct analogix_dp_device {
 	int			hpd_gpio;
 	bool                    force_hpd;
 	bool			psr_enable;
-	bool			fast_train_support;
+	bool			fast_train_enable;
 
 	struct mutex		panel_lock;
 	bool			panel_is_modeset;