linux-kernel - [PATCH AUTOSEL for 4.14 080/100] drm/bridge: tc358767: do no fail on hi-res displays

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Date:   Wed, 24 Jan 2018 04:15:06 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Andrey Gusakov <andrey.gusakov@...entembedded.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.14 080/100] drm/bridge: tc358767: do no fail on
 hi-res displays

From: Andrey Gusakov <andrey.gusakov@...entembedded.com>

[ Upstream commit cffd2b16c01c3431a7a7dd62e722af33490fc436 ]

Do not fail data rates higher than 2.7 and more than 2 lanes.
Try to fall back to 2.7Gbps and 2 lanes.

Acked-by: Philipp Zabel <p.zabel@...gutronix.de>
Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
Signed-off-by: Andrey Gusakov <andrey.gusakov@...entembedded.com>
Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1510073785-16108-2-git-send-email-andrey.gusakov@cogentembedded.com
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/gpu/drm/bridge/tc358767.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
index 8571cfd877c5..e1996dbfb0a1 100644
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -603,8 +603,15 @@ static int tc_get_display_props(struct tc_data *tc)
 	ret = drm_dp_link_probe(&tc->aux, &tc->link.base);
 	if (ret < 0)
 		goto err_dpcd_read;
-	if ((tc->link.base.rate != 162000) && (tc->link.base.rate != 270000))
-		goto err_dpcd_inval;
+	if (tc->link.base.rate != 162000 && tc->link.base.rate != 270000) {
+		dev_dbg(tc->dev, "Falling to 2.7 Gbps rate\n");
+		tc->link.base.rate = 270000;
+	}
+
+	if (tc->link.base.num_lanes > 2) {
+		dev_dbg(tc->dev, "Falling to 2 lanes\n");
+		tc->link.base.num_lanes = 2;
+	}
 
 	ret = drm_dp_dpcd_readb(&tc->aux, DP_MAX_DOWNSPREAD, tmp);
 	if (ret < 0)
@@ -637,9 +644,6 @@ static int tc_get_display_props(struct tc_data *tc)
 err_dpcd_read:
 	dev_err(tc->dev, "failed to read DPCD: %d\n", ret);
 	return ret;
-err_dpcd_inval:
-	dev_err(tc->dev, "invalid DPCD\n");
-	return -EINVAL;
 }
 
 static int tc_set_video_mode(struct tc_data *tc, struct drm_display_mode *mode)
-- 
2.11.0