As it turns out, apparently some machines will actually leave additional backlight functionality like dynamic backlight control on before the OS loads. Currently we don't take care to disable unsupported features when writing back the backlight mode, which can lead to some rather strange looking behavior when adjusting the backlight.
So, let's fix this by ensuring we only keep supported features enabled for panel backlights - which should fix some of the issues we were seeing from this on fi-bdw-samus.
Signed-off-by: Lyude Paul lyude@redhat.com Fixes: 867cf9cd73c3 ("drm/dp: Extract i915's eDP backlight code into DRM helpers") --- drivers/gpu/drm/drm_dp_helper.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 4d0d1e8e51fa..d9a7f07f42fd 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -3255,7 +3255,9 @@ int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct drm_edp_backli return ret < 0 ? ret : -EIO; }
- new_dpcd_buf = dpcd_buf; + /* Disable any backlight functionality we don't support that might be on */ + new_dpcd_buf = dpcd_buf & (DP_EDP_BACKLIGHT_CONTROL_MODE_MASK | + DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE);
if ((dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) != DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) { new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK; @@ -3277,6 +3279,8 @@ int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct drm_edp_backli aux->name, ret); else new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE; + } else { + new_dpcd_buf &= ~DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE; }
if (new_dpcd_buf != dpcd_buf) {