[PATCH 4.4 32/34] drm/amdgpu: fix DP mode validation

From: Greg Kroah-Hartman
Date: Sun Nov 13 2016 - 06:27:20 EST


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

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

From: Alex Deucher <alexander.deucher@xxxxxxx>

commit c47b9e0944e483309d66c807d650ac8b8ceafb57 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@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/drivers/gpu/drm/amd/amdgpu/atombios_dp.c
+++ b/drivers/gpu/drm/amd/amdgpu/atombios_dp.c
@@ -276,8 +276,8 @@ static int amdgpu_atombios_dp_get_dp_lin
}
}
} 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;