[Intel-gfx] [PATCH v5 3/9] drm/i915: Drop AUX backlight enable check for backlight control

[Pandiyan, Dhinakaran]

On Wed, 2017-05-10 at 13:05 +0300, Jani Nikula wrote:
> On Wed, 10 May 2017, "Pandiyan, Dhinakaran" <dhinakaran.pandiyan at intel.com> wrote:
> > On Tue, 2017-05-09 at 16:39 -0700, Puthikorn Voravootivat wrote:
> >> > How is backlight enabled in this case?
> >> Using eDP BL_ENABLE pin
> >
> >
> > Sure, but I am not seeing how this falls back to one of the
> > [bxt,lpt]_enable_backlight() functions in intel_panel.c. Apologies if I
> > am missing something very obvious.
> >
> > If intel_dp_aux_init_backlight_funcs() returned -ENODEV, then one of the
> > platform specific PWM enable callbacks would be called. But in this
> > case, dp_aux_enable_backlight() just returns without doing anything.
> 
> The eDP BL_ENABLE pin (in the physical eDP connector) is controlled by
> the panel power sequencer, independent from the PWM control. See
> intel_edp_backlight_* functions in intel_dp.c.
> 
> BR,
> Jani.
> 
> 

Ah! Thanks, that makes sense. The naming is a bit confusing though. The
_enable_backlight() functions in intel_panel.c don't enable backlight
but enable PWM.  



> >
> >
> > -DK
> >> 
> >> 
> >> On Sat, May 6, 2017 at 1:59 AM, Pandiyan, Dhinakaran
> >> <dhinakaran.pandiyan at intel.com> wrote:
> >>         On Wed, 2017-05-03 at 17:28 -0700, Puthikorn Voravootivat
> >>         wrote:
> >>         > There are some panel that
> >>         > (1) does not support display backlight enable via AUX
> >>         > (2) support display backlight adjustment via AUX
> >>         > (3) support display backlight enable via eDP BL_ENABLE pin
> >>         >
> >>         > The current driver required that (1) must be support to
> >>         enable (2).
> >>         > This patch drops that requirement.
> >>         >
> >>         > Signed-off-by: Puthikorn Voravootivat <puthik at chromium.org>
> >>         > ---
> >>         >  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 5 ++++-
> >>         >  1 file changed, 4 insertions(+), 1 deletion(-)
> >>         >
> >>         > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> >>         b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> >>         > index ad8560c5f689..5b83c9737644 100644
> >>         > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> >>         > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> >>         > @@ -28,6 +28,10 @@ static void
> >>         set_aux_backlight_enable(struct intel_dp *intel_dp, bool
> >>         enable)
> >>         >  {
> >>         >       uint8_t reg_val = 0;
> >>         >
> >>         > +       /* Early return when display use other mechanism to
> >>         enable backlight. */
> >>         > +     if (!(intel_dp->edp_dpcd[1] &
> >>         DP_EDP_BACKLIGHT_AUX_ENABLE_CAP))
> >>         > +             return;
> >>         > +
> >>         
> >>         How is backlight enabled in this case?
> >>         
> >>         -DK
> >>         
> >>         >       if (drm_dp_dpcd_readb(&intel_dp->aux,
> >>         DP_EDP_DISPLAY_CONTROL_REGISTER,
> >>         >                             &reg_val) < 0) {
> >>         >               DRM_DEBUG_KMS("Failed to read DPCD register 0x
> >>         %x\n",
> >>         > @@ -164,7 +168,6 @@
> >>         intel_dp_aux_display_control_capable(struct intel_connector
> >>         *connector)
> >>         >        * the panel can support backlight control over the
> >>         aux channel
> >>         >        */
> >>         >       if ((intel_dp->edp_dpcd[1] &
> >>         DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP) &&
> >>         > -         (intel_dp->edp_dpcd[1] &
> >>         DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
> >>         >           (intel_dp->edp_dpcd[2] &
> >>         DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) {
> >>         >               DRM_DEBUG_KMS("AUX Backlight Control
> >>         Supported!\n");
> >>         >               return true;
> >>         
> >>         
> >> 
> >> 
> >> _______________________________________________
> >> Intel-gfx mailing list
> >> Intel-gfx at lists.freedesktop.org
> >> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >
>