diff mbox

[RESEND,v4,3/6] drm/i915: Support dynamic backlight via DPCD register

Message ID 20170418234824.157355-4-puthik@chromium.org (mailing list archive)
State New, archived
Headers show

Commit Message

Puthikorn Voravootivat April 18, 2017, 11:48 p.m. UTC 
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.

Signed-off-by: Puthikorn Voravootivat <puthik@chromium.org>
---
 drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 31 +++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

Comments

Dhinakaran Pandiyan May 3, 2017, 3 a.m. UTC | #1 
On Tue, 2017-04-18 at 16:48 -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.



What does dynamic backlight do? I am trying to understand what allowing
0% minimum brightness means. 


> 

> Signed-off-by: Puthikorn Voravootivat <puthik@chromium.org>

> ---

>  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 31 +++++++++++++++++++++++----

>  1 file changed, 27 insertions(+), 4 deletions(-)

> 

> diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c

> index f06c8381c74e..ae1b6fe67feb 100644

> --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c

> +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c

> @@ -97,10 +97,24 @@ 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) };

> +	drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET,

> +			  dbc, sizeof(dbc));

> +}

> +

>  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;

>  

>  	set_aux_backlight_enable(intel_dp, true);

> @@ -110,16 +124,15 @@ 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;

> -		drm_dp_dpcd_writeb(&intel_dp->aux,

> -			DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf);

> +		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 */

> @@ -127,6 +140,16 @@ static void intel_dp_aux_enable_backlight(struct intel_connector *connector)

>  	default:

>  		break;

>  	}



Still need a switch here? You are setting mode as
DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD for all four values of mode. 



> +

> +	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);

> +	}


Should enabling dynamic backlight control be logged in debug messages?
Could be useful in case this turns out to be buggy.

-DK

> +

> +	if (new_dpcd_buf != dpcd_buf) {

> +		drm_dp_dpcd_writeb(&intel_dp->aux,

> +			DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf);

> +	}

>  }

>  

>  static void intel_dp_aux_disable_backlight(struct intel_connector *connector)
Puthikorn Voravootivat May 3, 2017, 10:16 p.m. UTC | #2 
On Tue, May 2, 2017 at 8:00 PM, Pandiyan, Dhinakaran <
dhinakaran.pandiyan@intel.com> wrote:

> On Tue, 2017-04-18 at 16:48 -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.
>
>
> What does dynamic backlight do? I am trying to understand what allowing
> 0% minimum brightness means.
>
> Display will make backlight dimmer when content shown on screen is darker.
See
https://www.ecnmag.com/article/2010/04/content-adaptive-lcd-backlight-control

>
> >
> > Signed-off-by: Puthikorn Voravootivat <puthik@chromium.org>
> > ---
> >  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 31
> +++++++++++++++++++++++----
> >  1 file changed, 27 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > index f06c8381c74e..ae1b6fe67feb 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > @@ -97,10 +97,24 @@ 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)
> };
> > +     drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_DBC_MINIMUM_BRIGHTNESS_
> SET,
> > +                       dbc, sizeof(dbc));
> > +}
> > +
> >  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;
> >
> >       set_aux_backlight_enable(intel_dp, true);
> > @@ -110,16 +124,15 @@ 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;
> > -             drm_dp_dpcd_writeb(&intel_dp->aux,
> > -                     DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf);
> > +             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 */
> > @@ -127,6 +140,16 @@ static void intel_dp_aux_enable_backlight(struct
> intel_connector *connector)
> >       default:
> >               break;
> >       }
>
>
> Still need a switch here? You are setting mode as
> DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD for all four values of mode.
>
>
>
> > +
> > +     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);
> > +     }
>
> Should enabling dynamic backlight control be logged in debug messages?
> Could be useful in case this turns out to be buggy.
>
Sure

>
> -DK
>
> > +
> > +     if (new_dpcd_buf != dpcd_buf) {
> > +             drm_dp_dpcd_writeb(&intel_dp->aux,
> > +                     DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf);
> > +     }
> >  }
> >
> >  static void intel_dp_aux_disable_backlight(struct intel_connector
> *connector)
>
>
diff mbox

Patch

diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
index f06c8381c74e..ae1b6fe67feb 100644
--- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
@@ -97,10 +97,24 @@  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) };
+	drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET,
+			  dbc, sizeof(dbc));
+}
+
 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;
 
 	set_aux_backlight_enable(intel_dp, true);
@@ -110,16 +124,15 @@  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;
-		drm_dp_dpcd_writeb(&intel_dp->aux,
-			DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf);
+		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 */
@@ -127,6 +140,16 @@  static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
 	default:
 		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);
+	}
+
+	if (new_dpcd_buf != dpcd_buf) {
+		drm_dp_dpcd_writeb(&intel_dp->aux,
+			DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf);
+	}
 }
 
 static void intel_dp_aux_disable_backlight(struct intel_connector *connector)