On Wed, 25 Sep 2013 20:18:39 +0300
Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote:
> On Wed, 25 Sep 2013, Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> wrote:
> > Still digging up the actual VBT info for this, but wanted to get this
> > out there for testing, or in case others are also bugged by this.
>
> I had a look at this a few weeks back. The VBT value for max backlight
> is in Hz (as is the value you get through opregion) and transforming
> that into the value the registers eat needs some digging. I tried, but
> none of the real world examples of VBT and PWM freq matched any of that,
> so I moved on...
>
> > This can happen if you boot with an external display connected. In that
> > case, the attached eDP backlight modulation frequency may not be
> > programmed, so we need to use something (in this case the value my BIOS
> > normally programs with just the internal display enabled).
>
> Something similar is required for non-vlv ChromeOS stuff too AFAIK.
>
> > Signed-off-by: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_panel.c | 17 +++++++++++++++++
> > 1 file changed, 17 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> > index 3bc89a6..a3536785 100644
> > --- a/drivers/gpu/drm/i915/intel_panel.c
> > +++ b/drivers/gpu/drm/i915/intel_panel.c
> > @@ -372,6 +372,9 @@ static u32 i915_read_blc_pwm_ctl(struct drm_device *dev)
> > I915_WRITE(BLC_PWM_CTL2,
> > dev_priv->regfile.saveBLC_PWM_CTL2);
> > }
> > +
> > + if (IS_VALLEYVIEW(dev) && !val)
> > + val = 0xffffffff;
>
> Huh, that's a lot... why don't you use the same value here and below?
>
> In fact, it should be sufficient to do the hack right here, as this gets
> called through intel_panel_setup_backlight(). Then again, this hole
> function is a kludge... :/
>
> > }
> >
> > return val;
> > @@ -629,10 +632,24 @@ set_level:
> > spin_unlock_irqrestore(&dev_priv->backlight.lock, flags);
> > }
> >
> > +/* FIXME: use VBT vals to init PWM_CTL and PWM_CTL2 correctly */
> > +static void intel_panel_init_backlight_regs(struct drm_device *dev)
> > +{
> > + struct drm_i915_private *dev_priv = dev->dev_private;
> > +
> > + if (IS_VALLEYVIEW(dev)) {
> > + u32 cur_val = I915_READ(BLC_PWM_CTL) &
> > + ~BACKLIGHT_DUTY_CYCLE_MASK;
>
> That should be without the NOT, right?
Oops yes, rather than preserving the value I'm about to clobber... :)
--
Jesse Barnes, Intel Open Source Technology Center
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