Re: [PATCH v10 1/3] drm/i915: Add heuristic to determine better way to adjust brightness

[Puthikorn Voravootivat <puthik@chromium.org>]

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On Fri, Jun 2, 2017 at 10:56 AM, Pandiyan, Dhinakaran <
dhinakaran.pandiyan@intel.com> wrote:

> On Fri, 2017-06-02 at 17:42 +0000, Pandiyan, Dhinakaran wrote:
>
> Somehow the CC's got removed in my previous reply, adding them back. See
> one additional comment below.
>
>
> > On Fri, 2017-05-26 at 18:42 -0700, Puthikorn Voravootivat wrote:
> > > Add heuristic to decide that AUX or PWM pin should use for
> > > backlight brightness adjustment and modify i915 param description
> > > to have auto, force disable, and force enable.
> > >
> > > The heuristic to determine that using AUX pin is better than using
> > > PWM pin is that the panel support any of the feature list here.
> > > - Regional backlight brightness adjustment
> > > - Backlight PWM frequency set
> > > - More than 8 bits resolution of brightness level
> > > - Backlight enablement via AUX and not by BL_ENABLE pin
> > >
> > > Signed-off-by: Puthikorn Voravootivat <puthik@chromium.org>
> > > ---
> > >  drivers/gpu/drm/i915/i915_params.c            |  7 +--
> > >  drivers/gpu/drm/i915/i915_params.h            |  2 +-
> > >  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 64
> +++++++++++++++++++++++++--
> > >  3 files changed, 66 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/i915_params.c
> b/drivers/gpu/drm/i915/i915_params.c
> > > index b6a7e363d076..3758ae1f11b4 100644
> > > --- a/drivers/gpu/drm/i915/i915_params.c
> > > +++ b/drivers/gpu/drm/i915/i915_params.c
> > > @@ -63,7 +63,7 @@ struct i915_params i915 __read_mostly = {
> > >     .huc_firmware_path = NULL,
> > >     .enable_dp_mst = true,
> > >     .inject_load_failure = 0,
> > > -   .enable_dpcd_backlight = false,
> > > +   .enable_dpcd_backlight = -1,
> > >     .enable_gvt = false,
> > >  };
> > >
> > > @@ -246,9 +246,10 @@ MODULE_PARM_DESC(enable_dp_mst,
> > >  module_param_named_unsafe(inject_load_failure,
> i915.inject_load_failure, uint, 0400);
> > >  MODULE_PARM_DESC(inject_load_failure,
> > >     "Force an error after a number of failure check points (0:disabled
> (default), N:force failure at the Nth failure check point)");
> > > -module_param_named(enable_dpcd_backlight,
> i915.enable_dpcd_backlight, bool, 0600);
> > > +module_param_named_unsafe(enable_dpcd_backlight,
> i915.enable_dpcd_backlight, int, 0600);
> > >  MODULE_PARM_DESC(enable_dpcd_backlight,
> > > -   "Enable support for DPCD backlight control (default:false)");
> > > +   "Enable support for DPCD backlight control "
> > > +   "(-1:auto (default), 0:force disable, 1:force enabled if
> supported");
> > >
> > >  module_param_named(enable_gvt, i915.enable_gvt, bool, 0400);
> > >  MODULE_PARM_DESC(enable_gvt,
> > > diff --git a/drivers/gpu/drm/i915/i915_params.h
> b/drivers/gpu/drm/i915/i915_params.h
> > > index 34148cc8637c..ac02efce6e22 100644
> > > --- a/drivers/gpu/drm/i915/i915_params.h
> > > +++ b/drivers/gpu/drm/i915/i915_params.h
> > > @@ -66,7 +66,7 @@
> > >     func(bool, verbose_state_checks); \
> > >     func(bool, nuclear_pageflip); \
> > >     func(bool, enable_dp_mst); \
> > > -   func(bool, enable_dpcd_backlight); \
> > > +   func(int, enable_dpcd_backlight); \
>
>
> Please move this above the bools, see comment in code that's a few lines
> above.
>
> Will do


> -DK
>
> > >     func(bool, enable_gvt)
> > >
> > >  #define MEMBER(T, member) T member
> > > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > index a0995c00fc84..c89aae804659 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > @@ -43,6 +43,9 @@ static void set_aux_backlight_enable(struct
> intel_dp *intel_dp, bool enable)
> > >     else
> > >             reg_val &= ~(DP_EDP_BACKLIGHT_ENABLE);
> > >
> > > +   /* TODO: If the panel also support enabling backlight via
> BL_ENABLE pin,
> > > +    * the backlight will be enabled again in _intel_edp_backlight_on()
> > > +    */
> >
> > Unrelated hunk, please remove. This should have been included in one of
> > the previous patches.
>
Removed


> >
> > >     if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_DISPLAY_CONTROL_
> REGISTER,
> > >                            reg_val) != 1) {
> > >             DRM_DEBUG_KMS("Failed to %s aux backlight\n",
> > > @@ -168,15 +171,66 @@ intel_dp_aux_display_control_capable(struct
> intel_connector *connector)
> > >     /* Check the  eDP Display control capabilities registers to
> determine if
> > >      * 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[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)
> &&
> > > -       !(intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP))
> {
> > > +   if ((intel_dp->edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP)
> &&
> > > +       (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP))
> {
> > >             DRM_DEBUG_KMS("AUX Backlight Control Supported!\n");
> > >             return true;
> > >     }
> > >     return false;
> > >  }
> > >
> > > +/*
> > > + * Heuristic function whether we should use AUX for backlight
> adjustment or not.
> > > + *
> > > + * We should use AUX for backlight brightness adjustment if panel
> doesn't this
> > > + * via PWM pin or using AUX is better than using PWM pin.
> > > + *
> > > + * The heuristic to determine that using AUX pin is better than using
> PWM pin is
> > > + * that the panel support any of the feature list here.
> > > + * - Regional backlight brightness adjustment
> > > + * - Backlight PWM frequency set
> > > + * - More than 8 bits resolution of brightness level
> > > + * - Backlight enablement via AUX and not by BL_ENABLE pin
> > > + *
> > > + * If all above are not true, assume that using PWM pin is better.
> > > + */
> > > +static bool
> > > +intel_dp_aux_display_control_heuristic(struct intel_connector
> *connector)
> > > +{
> > > +   struct intel_dp *intel_dp = enc_to_intel_dp(&connector->
> encoder->base);
> > > +   uint8_t reg_val;
> > > +
> > > +   /* Panel doesn't support adjusting backlight brightness via PWN
> pin */
> > > +   if (!(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_BRIGHTNESS_
> PWM_PIN_CAP))
> >
> > Isn't BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP in edp_dpcd[2] ?
> >
>
Thank you for catching this.

> >
> > > +           return true;
> > > +
> > > +   /* Panel supports regional backlight brightness adjustment */
> > > +   if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_GENERAL_CAP_3,
> >
> > Spec says this register is new to eDP 1.4. I don't see a check for
> > version.
> >
>
There is no need to check this. In not supported eDP panel, this register
will read all 0s.

> >
> > > +                         &reg_val) != 1) {
> > > +           DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
> > > +                          DP_EDP_GENERAL_CAP_3);
> > > +           return false;
> > > +   }
> > > +   if (reg_val > 0)
> > > +           return true;
> > > +
> > > +   /* Panel supports backlight PWM frequency set */
> > > +   if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP)
> > > +           return true;
> > > +
> > > +   /* Panel supports more than 8 bits resolution of brightness level
> */
> > > +   if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_
> BYTE_COUNT)
> > > +           return true;
> >
> > I don't know if more than 8 bits is relatively better than the
> > resolution PWM pin allows. I guess, we could fix that later by comparing
> > the number of brightness levels.
> >
> > > +
> > > +   /* Panel supports enabling backlight via AUX but not by BL_ENABLE
> pin */
> > > +   if ((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
> > > +       !(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_PIN_ENABLE_CAP))
> > > +           return true;
> > > +
> > > +   return false;
> > > +
> > > +}
> > > +
> > >  int intel_dp_aux_init_backlight_funcs(struct intel_connector
> *intel_connector)
> > >  {
> > >     struct intel_panel *panel = &intel_connector->panel;
> > > @@ -187,6 +241,10 @@ int intel_dp_aux_init_backlight_funcs(struct
> intel_connector *intel_connector)
> > >     if (!intel_dp_aux_display_control_capable(intel_connector))
> > >             return -ENODEV;
> > >
> > > +   if (i915.enable_dpcd_backlight == -1 &&
> > > +       !intel_dp_aux_display_control_heuristic(intel_connector))
> > > +           return -ENODEV;
> > > +
> > >     panel->backlight.setup = intel_dp_aux_setup_backlight;
> > >     panel->backlight.enable = intel_dp_aux_enable_backlight;
> > >     panel->backlight.disable = intel_dp_aux_disable_backlight;
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
>

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