[Intel-gfx] [PATCH v5 6/9] drm/i915: Support dynamic backlight via DPCD register

[Puthikorn Voravootivat]

Fair enough. Will add kernel switch in next version.

On Wed, May 10, 2017 at 6:26 PM, Pandiyan, Dhinakaran <
dhinakaran.pandiyan at intel.com> wrote:

> On Wed, 2017-05-03 at 17:28 -0700, Puthikorn Voravootivat wrote:
> > This patch enables dynamic backlight by default for eDP
> > panel that supports this feature via DPCD register and
> > set minimum / maximum brightness to 0% and 100% of the
> > normal brightness.
>
>
> I read the link that you shared last time, should there be a switch for
> a feature like this that can affect image quality? Should this be a
> decision in the kernel with no provision to turn off/on?
>
>
> -DK
>
> >
> > Signed-off-by: Puthikorn Voravootivat <puthik at chromium.org>
> > ---
> >  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 39
> ++++++++++++++++++++++-----
> >  1 file changed, 33 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > index 5ef3ade7c40e..7d323af96636 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > @@ -97,10 +97,27 @@ intel_dp_aux_set_backlight(struct intel_connector
> *connector, u32 level)
> >       }
> >  }
> >
> > +/*
> > + * Set minimum / maximum dynamic brightness percentage. This value is
> expressed
> > + * as the percentage of normal brightness in 5% increments.
> > + */
> > +static void
> > +intel_dp_aux_set_dynamic_backlight_percent(struct intel_dp *intel_dp,
> > +                                        u32 min, u32 max)
> > +{
> > +     u8 dbc[] = { DIV_ROUND_CLOSEST(min, 5), DIV_ROUND_CLOSEST(max, 5)
> };
> > +
> > +     if (drm_dp_dpcd_write(&intel_dp->aux,
> DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET,
> > +                       dbc, sizeof(dbc) < 0)) {
> > +             DRM_DEBUG_KMS("Failed to write aux DBC brightness
> level\n");
> > +     }
> > +}
> > +
> >  static void intel_dp_aux_enable_backlight(struct intel_connector
> *connector)
> >  {
> >       struct intel_dp *intel_dp = enc_to_intel_dp(&connector->
> encoder->base);
> >       uint8_t dpcd_buf = 0;
> > +     uint8_t new_dpcd_buf = 0;
> >       uint8_t edp_backlight_mode = 0;
> >
> >       if (drm_dp_dpcd_readb(&intel_dp->aux,
> > @@ -110,18 +127,15 @@ static void intel_dp_aux_enable_backlight(struct
> intel_connector *connector)
> >               return;
> >       }
> >
> > +     new_dpcd_buf = dpcd_buf;
> >       edp_backlight_mode = dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_
> MASK;
> >
> >       switch (edp_backlight_mode) {
> >       case DP_EDP_BACKLIGHT_CONTROL_MODE_PWM:
> >       case DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET:
> >       case DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT:
> > -             dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
> > -             dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > -             if (drm_dp_dpcd_writeb(&intel_dp->aux,
> > -                     DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf) <
> 0) {
> > -                     DRM_DEBUG_KMS("Failed to write aux backlight
> mode\n");
> > -             }
> > +             new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
> > +             new_dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> >               break;
> >
> >       /* Do nothing when it is already DPCD mode */
> > @@ -130,6 +144,19 @@ static void intel_dp_aux_enable_backlight(struct
> intel_connector *connector)
> >               break;
> >       }
> >
> > +     if (intel_dp->edp_dpcd[2] & DP_EDP_DYNAMIC_BACKLIGHT_CAP) {
> > +             new_dpcd_buf |= DP_EDP_DYNAMIC_BACKLIGHT_ENABLE;
> > +             intel_dp_aux_set_dynamic_backlight_percent(intel_dp, 0,
> 100);
> > +             DRM_DEBUG_KMS("Enable dynamic brightness.\n");
> > +     }
> > +
> > +     if (new_dpcd_buf != dpcd_buf) {
> > +             if (drm_dp_dpcd_writeb(&intel_dp->aux,
> > +                     DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf)
> < 0) {
> > +                     DRM_DEBUG_KMS("Failed to write aux backlight
> mode\n");
> > +             }
> > +     }
> > +
> >       set_aux_backlight_enable(intel_dp, true);
> >  }
> >
>
>
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