drm/dp: WARN about invalid/unknown link rates and bw codes

Falling back to the lowest value is likely the only thing we can do, but
doing it silently seems like a bad thing to do. Catch it early and make
loud noises.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171009092959.29021-1-jani.nikula@intel.com

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 08af8d6b844b67e0653f93c5dc012706d9a13b19..b3d68964b407677148f11551dababb0d7cb71853 100644 (file)
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -137,8 +137,10 @@ EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
 u8 drm_dp_link_rate_to_bw_code(int link_rate)
 {
        switch (link_rate) {
-       case 162000:
        default:
+               WARN(1, "unknown DP link rate %d, using %x\n", link_rate,
+                    DP_LINK_BW_1_62);
+       case 162000:
                return DP_LINK_BW_1_62;
        case 270000:
                return DP_LINK_BW_2_7;
@@ -151,8 +153,9 @@ EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code);
 int drm_dp_bw_code_to_link_rate(u8 link_bw)
 {
        switch (link_bw) {
-       case DP_LINK_BW_1_62:
        default:
+               WARN(1, "unknown DP link BW code %x, using 162000\n", link_bw);
+       case DP_LINK_BW_1_62:
                return 162000;
        case DP_LINK_BW_2_7:
                return 270000;