linux-kernel - [PATCH 4.4 34/34] drm/radeon: fix DP mode validation

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Message-Id: <20161113112401.580850723@linuxfoundation.org>
Date:   Sun, 13 Nov 2016 12:25:06 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alex Deucher <alexander.deucher@....com>
Subject: [PATCH 4.4 34/34] drm/radeon: fix DP mode validation

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alex Deucher <alexander.deucher@....com>

commit ff0bd441bdfbfa09d05fdba9829a0401a46635c1 upstream.

Switch the order of the loops to walk the rates on the top
so we exhaust all DP 1.1 rate/lane combinations before trying
DP 1.2 rate/lane combos.

This avoids selecting rates that are supported by the monitor,
but not the connector leading to valid modes getting rejected.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=95206

Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/radeon/atombios_dp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -326,8 +326,8 @@ int radeon_dp_get_dp_link_config(struct
 			}
 		}
 	} else {
-		for (lane_num = 1; lane_num <= max_lane_num; lane_num <<= 1) {
-			for (i = 0; i < ARRAY_SIZE(link_rates) && link_rates[i] <= max_link_rate; i++) {
+		for (i = 0; i < ARRAY_SIZE(link_rates) && link_rates[i] <= max_link_rate; i++) {
+			for (lane_num = 1; lane_num <= max_lane_num; lane_num <<= 1) {
 				max_pix_clock = (lane_num * link_rates[i] * 8) / bpp;
 				if (max_pix_clock >= pix_clock) {
 					*dp_lanes = lane_num;