| Message ID | 20191122231616.2574-4-lyude@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915: eDP DPCD aux backlight fixes | expand |
On Fri, 22 Nov 2019, Lyude Paul <lyude@redhat.com> wrote: > For eDP panels, it appears it's expected that so long as the panel is in > DPCD control mode that the brightness value is never set to 0. Instead, > if the desired effect is to set the panel's backlight to 0 we're > expected to simply turn off the backlight through the > DP_EDP_DISPLAY_CONTROL_REGISTER. > > We already do the latter correctly in intel_dp_aux_disable_backlight(). > But, we make the mistake of writing the DPCD registers in the wrong > order when enabling the backlight in intel_dp_aux_enable_backlight() > since we currently enable the backlight through > DP_EDP_DISPLAY_CONTROL_REGISTER before writing the brightness level. On > the X1 Extreme 2nd Generation, this appears to have the potential of > confusing the panel in such a way that further attempts to set the > brightness don't actually change the backlight as expected and leave it > off. Presumably, this happens because the incorrect register writing > order briefly leaves the panel with DPCD mode enabled and a 0 brightness > level set. > > So, reverse the order we write the DPCD registers when enabling the > panel backlight so that we write the brightness value first, and enable > the backlight second. This fix appears to be the final bit needed to get > the backlight on the ThinkPad X1 Extreme 2nd Generation's AMOLED screen > working. > > Signed-off-by: Lyude Paul <lyude@redhat.com> Reviewed-by: Jani Nikula <jani.nikula@intel.com> > --- > drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > index 0bf8772bc7bb..87b59db9ffe3 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > @@ -205,8 +205,9 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st > } > } > > + intel_dp_aux_set_backlight(conn_state, > + connector->panel.backlight.level); > set_aux_backlight_enable(intel_dp, true); > - intel_dp_aux_set_backlight(conn_state, connector->panel.backlight.level); > } > > static void intel_dp_aux_disable_backlight(const struct drm_connector_state *old_conn_state)
On 11/22/19 6:16 PM, Lyude Paul wrote: > For eDP panels, it appears it's expected that so long as the panel is in > DPCD control mode that the brightness value is never set to 0. Instead, > if the desired effect is to set the panel's backlight to 0 we're > expected to simply turn off the backlight through the > DP_EDP_DISPLAY_CONTROL_REGISTER. > > We already do the latter correctly in intel_dp_aux_disable_backlight(). > But, we make the mistake of writing the DPCD registers in the wrong > order when enabling the backlight in intel_dp_aux_enable_backlight() > since we currently enable the backlight through > DP_EDP_DISPLAY_CONTROL_REGISTER before writing the brightness level. On > the X1 Extreme 2nd Generation, this appears to have the potential of > confusing the panel in such a way that further attempts to set the > brightness don't actually change the backlight as expected and leave it > off. Presumably, this happens because the incorrect register writing > order briefly leaves the panel with DPCD mode enabled and a 0 brightness > level set. > > So, reverse the order we write the DPCD registers when enabling the > panel backlight so that we write the brightness value first, and enable > the backlight second. This fix appears to be the final bit needed to get > the backlight on the ThinkPad X1 Extreme 2nd Generation's AMOLED screen > working. > > Signed-off-by: Lyude Paul <lyude@redhat.com> > Reviewed-by: Jani Nikula <jani.nikula@intel.com> > --- > drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > index 0bf8772bc7bb..87b59db9ffe3 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > @@ -205,8 +205,9 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st > } > } > > + intel_dp_aux_set_backlight(conn_state, > + connector->panel.backlight.level); > set_aux_backlight_enable(intel_dp, true); > - intel_dp_aux_set_backlight(conn_state, connector->panel.backlight.level); > } > > static void intel_dp_aux_disable_backlight(const struct drm_connector_state *old_conn_state) > Tested-by:Perry Yuan <pyuan@redhat.com>
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 0bf8772bc7bb..87b59db9ffe3 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -205,8 +205,9 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st } } + intel_dp_aux_set_backlight(conn_state, + connector->panel.backlight.level); set_aux_backlight_enable(intel_dp, true); - intel_dp_aux_set_backlight(conn_state, connector->panel.backlight.level); } static void intel_dp_aux_disable_backlight(const struct drm_connector_state *old_conn_state)
For eDP panels, it appears it's expected that so long as the panel is in DPCD control mode that the brightness value is never set to 0. Instead, if the desired effect is to set the panel's backlight to 0 we're expected to simply turn off the backlight through the DP_EDP_DISPLAY_CONTROL_REGISTER. We already do the latter correctly in intel_dp_aux_disable_backlight(). But, we make the mistake of writing the DPCD registers in the wrong order when enabling the backlight in intel_dp_aux_enable_backlight() since we currently enable the backlight through DP_EDP_DISPLAY_CONTROL_REGISTER before writing the brightness level. On the X1 Extreme 2nd Generation, this appears to have the potential of confusing the panel in such a way that further attempts to set the brightness don't actually change the backlight as expected and leave it off. Presumably, this happens because the incorrect register writing order briefly leaves the panel with DPCD mode enabled and a 0 brightness level set. So, reverse the order we write the DPCD registers when enabling the panel backlight so that we write the brightness value first, and enable the backlight second. This fix appears to be the final bit needed to get the backlight on the ThinkPad X1 Extreme 2nd Generation's AMOLED screen working. Signed-off-by: Lyude Paul <lyude@redhat.com> --- drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)