drm/amdgpu: fix DP mode validation

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@amd.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_dp.c b/drivers/gpu/drm/amd/amdgpu/atombios_dp.c
index bf731e9..7f85c2c 100644 (file)
--- 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_link_config(struct drm_connector *connector
                        }
                }
        } 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;