Re: [Intel-gfx] [PATCH v5 9/9] drm/i915: Set PWM divider to match desired frequency in vbt

2017-05-08 Thread Puthikorn Voravootivat 
Actually you are right. Sorry it's my mistake.
I was focusing on make the actual frequency match the desired frequency as
much as possible.
But more granularity in backlight adjustment probably more important than
that.

Will submit new version of this patch to fix this.

On Mon, May 8, 2017 at 11:17 AM, Pandiyan, Dhinakaran <
dhinakaran.pandi...@intel.com> wrote:

> On Mon, 2017-05-08 at 10:49 -0700, Puthikorn Voravootivat wrote:
> > This is not related to brightness control. This calculation is used to
> > set the PWM frequency.
> > Frequency = 27 Mhz / (F * 2^ Pn)
> >
> > Lower Pn means higher value for F which mean more accuracy for this
> > calculation.
>
> I am not sure I follow this. Quoting from the spec -
> "A larger Pn value (meaning more PWM generator control bits) provides a
> finer backlight adjustment (increased  granularity),  but  also  limits
> the  maximum  backlight  frequency,  as  described in this   section."
>
> and then again
>
> "Allowing Pn to be adjustable provides the flexibility of backlight
> dimming granularity vs. maximum backlight frequency."
>
> >
> > On Sat, May 6, 2017 at 1:35 AM, Pandiyan, Dhinakaran
> >  wrote:
> > On Wed, 2017-05-03 at 17:28 -0700, Puthikorn Voravootivat
> > wrote:
> > > Read desired PWM frequency from panel vbt and calculate the
> > > value for divider in DPCD address 0x724 and 0x728 to match
> > > that frequency as close as possible.
> > >
> > > Signed-off-by: Puthikorn Voravootivat 
> > > ---
> > >  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 71
> > +++
> > >  1 file changed, 71 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > index fc26fea94fd4..441ad434a82b 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > @@ -113,12 +113,76 @@
> > intel_dp_aux_set_dynamic_backlight_percent(struct intel_dp
> > *intel_dp,
> > >   }
> > >  }
> > >
> > > +/*
> > > + * Set PWM Frequency divider to match desired frequency in
> > vbt.
> > > + * The PWM Frequency is calculated as 27Mhz / (F x P).
> > > + * - Where F = PWM Frequency Pre-Divider value programmed
> > by field 7:0 of the
> > > + * EDP_BACKLIGHT_FREQ_SET register (DPCD
> > Address 00728h)
> > > + * - Where P = 2^Pn, where Pn is the value programmed by
> > field 4:0 of the
> > > + * EDP_PWMGEN_BIT_COUNT register (DPCD Address
> > 00724h)
> > > + */
> > > +static void intel_dp_aux_set_pwm_freq(struct
> > intel_connector *connector)
> > > +{
> > > + struct drm_i915_private *dev_priv =
> > to_i915(connector->base.dev);
> > > + struct intel_dp *intel_dp =
> > enc_to_intel_dp(>encoder->base);
> > > + int freq, fxp, f;
> > > + u8 pn, pn_min, pn_max;
> > > +
> > > + /* Find desired value of (F x P)
> > > +  * Note that, if F x P is out of supported range, the
> > maximum value or
> > > +  * minimum value will applied automatically. So no
> > need to check that.
> > > +  */
> > > + freq = dev_priv->vbt.backlight.pwm_freq_hz;
> > > + DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz
> > \n", freq);
> > > + if (!freq) {
> > > + DRM_DEBUG_KMS("Use panel default backlight
> > frequency\n");
> > > + return;
> > > + }
> > > +
> > > + fxp = DP_EDP_BACKLIGHT_FREQ_BASE / freq;
> > > +
> > > + /* Use lowest possible value of Pn to try to make F to
> > be between 1 and
> >
> >
> > What's the reason to use the lowest possible value of Pn? From
> > what I
> > understand, choosing a higher value of Pn offers more steps
> > for
> > brightness control.
> >
> > -DK
> >
> > > +  * 255 while still in the range Pn_min and Pn_max
> > > +  */
> > > + if (drm_dp_dpcd_readb(_dp->aux,
> > > +
> > DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, _min) != 1) {
> > > + DRM_DEBUG_KMS("Failed to read pwmgen bit count
> > cap min\n");
> > > + return;
> > > + }
> > > + if (drm_dp_dpcd_readb(_dp->aux,
> > > +
> > DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, _max) != 1) {
> > > + DRM_DEBUG_KMS("Failed to read pwmgen bit count
> > cap max\n");
> > > + return;
> > > +

Re: [Intel-gfx] [PATCH v5 9/9] drm/i915: Set PWM divider to match desired frequency in vbt

2017-05-08 Thread Pandiyan, Dhinakaran 
On Mon, 2017-05-08 at 10:49 -0700, Puthikorn Voravootivat wrote:
> This is not related to brightness control. This calculation is used to
> set the PWM frequency.
> Frequency = 27 Mhz / (F * 2^ Pn)
> 
> Lower Pn means higher value for F which mean more accuracy for this
> calculation.

I am not sure I follow this. Quoting from the spec - 
"A larger Pn value (meaning more PWM generator control bits) provides a
finer backlight adjustment (increased  granularity),  but  also  limits
the  maximum  backlight  frequency,  as  described in this   section."

and then again

"Allowing Pn to be adjustable provides the flexibility of backlight
dimming granularity vs. maximum backlight frequency."
 
> 
> On Sat, May 6, 2017 at 1:35 AM, Pandiyan, Dhinakaran
>  wrote:
> On Wed, 2017-05-03 at 17:28 -0700, Puthikorn Voravootivat
> wrote:
> > Read desired PWM frequency from panel vbt and calculate the
> > value for divider in DPCD address 0x724 and 0x728 to match
> > that frequency as close as possible.
> >
> > Signed-off-by: Puthikorn Voravootivat 
> > ---
> >  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 71
> +++
> >  1 file changed, 71 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > index fc26fea94fd4..441ad434a82b 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > @@ -113,12 +113,76 @@
> intel_dp_aux_set_dynamic_backlight_percent(struct intel_dp
> *intel_dp,
> >   }
> >  }
> >
> > +/*
> > + * Set PWM Frequency divider to match desired frequency in
> vbt.
> > + * The PWM Frequency is calculated as 27Mhz / (F x P).
> > + * - Where F = PWM Frequency Pre-Divider value programmed
> by field 7:0 of the
> > + * EDP_BACKLIGHT_FREQ_SET register (DPCD
> Address 00728h)
> > + * - Where P = 2^Pn, where Pn is the value programmed by
> field 4:0 of the
> > + * EDP_PWMGEN_BIT_COUNT register (DPCD Address
> 00724h)
> > + */
> > +static void intel_dp_aux_set_pwm_freq(struct
> intel_connector *connector)
> > +{
> > + struct drm_i915_private *dev_priv =
> to_i915(connector->base.dev);
> > + struct intel_dp *intel_dp =
> enc_to_intel_dp(>encoder->base);
> > + int freq, fxp, f;
> > + u8 pn, pn_min, pn_max;
> > +
> > + /* Find desired value of (F x P)
> > +  * Note that, if F x P is out of supported range, the
> maximum value or
> > +  * minimum value will applied automatically. So no
> need to check that.
> > +  */
> > + freq = dev_priv->vbt.backlight.pwm_freq_hz;
> > + DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz
> \n", freq);
> > + if (!freq) {
> > + DRM_DEBUG_KMS("Use panel default backlight
> frequency\n");
> > + return;
> > + }
> > +
> > + fxp = DP_EDP_BACKLIGHT_FREQ_BASE / freq;
> > +
> > + /* Use lowest possible value of Pn to try to make F to
> be between 1 and
> 
> 
> What's the reason to use the lowest possible value of Pn? From
> what I
> understand, choosing a higher value of Pn offers more steps
> for
> brightness control.
> 
> -DK
> 
> > +  * 255 while still in the range Pn_min and Pn_max
> > +  */
> > + if (drm_dp_dpcd_readb(_dp->aux,
> > +
> DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, _min) != 1) {
> > + DRM_DEBUG_KMS("Failed to read pwmgen bit count
> cap min\n");
> > + return;
> > + }
> > + if (drm_dp_dpcd_readb(_dp->aux,
> > +
> DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, _max) != 1) {
> > + DRM_DEBUG_KMS("Failed to read pwmgen bit count
> cap max\n");
> > + return;
> > + }
> > + pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > + pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > +
> > + f = fxp >> pn_min;
> > +
> > + for (pn = pn_min; pn < pn_max && f > 255; pn++)
> > + f >>= 1;
> > +
> > + f = clamp(f, 1, 255);
> > +
> > + if (drm_dp_dpcd_writeb(_dp->aux,
> > +DP_EDP_PWMGEN_BIT_COUNT, pn) <
> 0) {
> > + DRM_DEBUG_KMS("Failed to write

Re: [Intel-gfx] [PATCH v5 9/9] drm/i915: Set PWM divider to match desired frequency in vbt

2017-05-08 Thread Puthikorn Voravootivat 
This is not related to brightness control. This calculation is used to set
the PWM frequency.
Frequency = 27 Mhz / (F * 2^ Pn)
Lower Pn means higher value for F which mean more accuracy for this
calculation.


On Sat, May 6, 2017 at 1:35 AM, Pandiyan, Dhinakaran <
dhinakaran.pandi...@intel.com> wrote:

> On Wed, 2017-05-03 at 17:28 -0700, Puthikorn Voravootivat wrote:
> > Read desired PWM frequency from panel vbt and calculate the
> > value for divider in DPCD address 0x724 and 0x728 to match
> > that frequency as close as possible.
> >
> > Signed-off-by: Puthikorn Voravootivat 
> > ---
> >  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 71
> +++
> >  1 file changed, 71 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > index fc26fea94fd4..441ad434a82b 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > @@ -113,12 +113,76 @@ intel_dp_aux_set_dynamic_backlight_percent(struct
> intel_dp *intel_dp,
> >   }
> >  }
> >
> > +/*
> > + * Set PWM Frequency divider to match desired frequency in vbt.
> > + * The PWM Frequency is calculated as 27Mhz / (F x P).
> > + * - Where F = PWM Frequency Pre-Divider value programmed by field 7:0
> of the
> > + * EDP_BACKLIGHT_FREQ_SET register (DPCD Address 00728h)
> > + * - Where P = 2^Pn, where Pn is the value programmed by field 4:0 of
> the
> > + * EDP_PWMGEN_BIT_COUNT register (DPCD Address 00724h)
> > + */
> > +static void intel_dp_aux_set_pwm_freq(struct intel_connector
> *connector)
> > +{
> > + struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
> > + struct intel_dp *intel_dp = enc_to_intel_dp(>
> encoder->base);
> > + int freq, fxp, f;
> > + u8 pn, pn_min, pn_max;
> > +
> > + /* Find desired value of (F x P)
> > +  * Note that, if F x P is out of supported range, the maximum
> value or
> > +  * minimum value will applied automatically. So no need to check
> that.
> > +  */
> > + freq = dev_priv->vbt.backlight.pwm_freq_hz;
> > + DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz\n", freq);
> > + if (!freq) {
> > + DRM_DEBUG_KMS("Use panel default backlight frequency\n");
> > + return;
> > + }
> > +
> > + fxp = DP_EDP_BACKLIGHT_FREQ_BASE / freq;
> > +
> > + /* Use lowest possible value of Pn to try to make F to be between
> 1 and
>
> What's the reason to use the lowest possible value of Pn? From what I
> understand, choosing a higher value of Pn offers more steps for
> brightness control.
>
> -DK
>
> > +  * 255 while still in the range Pn_min and Pn_max
> > +  */
> > + if (drm_dp_dpcd_readb(_dp->aux,
> > +DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, _min)
> != 1) {
> > + DRM_DEBUG_KMS("Failed to read pwmgen bit count cap min\n");
> > + return;
> > + }
> > + if (drm_dp_dpcd_readb(_dp->aux,
> > +DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, _max)
> != 1) {
> > + DRM_DEBUG_KMS("Failed to read pwmgen bit count cap max\n");
> > + return;
> > + }
> > + pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > + pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > +
> > + f = fxp >> pn_min;
> > +
> > + for (pn = pn_min; pn < pn_max && f > 255; pn++)
> > + f >>= 1;
> > +
> > + f = clamp(f, 1, 255);
> > +
> > + if (drm_dp_dpcd_writeb(_dp->aux,
> > +DP_EDP_PWMGEN_BIT_COUNT, pn) < 0) {
> > + DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n");
> > + return;
> > + }
> > + if (drm_dp_dpcd_writeb(_dp->aux,
> > +DP_EDP_BACKLIGHT_FREQ_SET, (u8) f) < 0) {
> > + DRM_DEBUG_KMS("Failed to write aux backlight freq\n");
> > + return;
> > + }
> > +}
> > +
> >  static void intel_dp_aux_enable_backlight(struct intel_connector
> *connector)
> >  {
> >   struct intel_dp *intel_dp = enc_to_intel_dp(>
> encoder->base);
> >   uint8_t dpcd_buf = 0;
> >   uint8_t new_dpcd_buf = 0;
> >   uint8_t edp_backlight_mode = 0;
> > + bool freq_cap;
> >
> >   if (drm_dp_dpcd_readb(_dp->aux,
> >   DP_EDP_BACKLIGHT_MODE_SET_REGISTER, _buf) !=
> 1) {
> > @@ -150,6 +214,10 @@ static void intel_dp_aux_enable_backlight(struct
> intel_connector *connector)
> >   DRM_DEBUG_KMS("Enable dynamic brightness.\n");
> >   }
> >
> > + freq_cap = intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_
> CAP;
> > + if (freq_cap)
> > + new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
> > +
> >   if (new_dpcd_buf != dpcd_buf) {
> >   if (drm_dp_dpcd_writeb(_dp->aux,
> >   DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf)
> < 0) {
> > @@ -157,6 +225,9 @@ static

Re: [Intel-gfx] [PATCH v5 9/9] drm/i915: Set PWM divider to match desired frequency in vbt

2017-05-06 Thread Pandiyan, Dhinakaran 
On Wed, 2017-05-03 at 17:28 -0700, Puthikorn Voravootivat wrote:
> Read desired PWM frequency from panel vbt and calculate the
> value for divider in DPCD address 0x724 and 0x728 to match
> that frequency as close as possible.
> 
> Signed-off-by: Puthikorn Voravootivat 
> ---
>  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 71 
> +++
>  1 file changed, 71 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c 
> b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> index fc26fea94fd4..441ad434a82b 100644
> --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> @@ -113,12 +113,76 @@ intel_dp_aux_set_dynamic_backlight_percent(struct 
> intel_dp *intel_dp,
>   }
>  }
>  
> +/*
> + * Set PWM Frequency divider to match desired frequency in vbt.
> + * The PWM Frequency is calculated as 27Mhz / (F x P).
> + * - Where F = PWM Frequency Pre-Divider value programmed by field 7:0 of the
> + * EDP_BACKLIGHT_FREQ_SET register (DPCD Address 00728h)
> + * - Where P = 2^Pn, where Pn is the value programmed by field 4:0 of the
> + * EDP_PWMGEN_BIT_COUNT register (DPCD Address 00724h)
> + */
> +static void intel_dp_aux_set_pwm_freq(struct intel_connector *connector)
> +{
> + struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
> + struct intel_dp *intel_dp = enc_to_intel_dp(>encoder->base);
> + int freq, fxp, f;
> + u8 pn, pn_min, pn_max;
> +
> + /* Find desired value of (F x P)
> +  * Note that, if F x P is out of supported range, the maximum value or
> +  * minimum value will applied automatically. So no need to check that.
> +  */
> + freq = dev_priv->vbt.backlight.pwm_freq_hz;
> + DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz\n", freq);
> + if (!freq) {
> + DRM_DEBUG_KMS("Use panel default backlight frequency\n");
> + return;
> + }
> +
> + fxp = DP_EDP_BACKLIGHT_FREQ_BASE / freq;
> +
> + /* Use lowest possible value of Pn to try to make F to be between 1 and

What's the reason to use the lowest possible value of Pn? From what I
understand, choosing a higher value of Pn offers more steps for
brightness control.

-DK

> +  * 255 while still in the range Pn_min and Pn_max
> +  */
> + if (drm_dp_dpcd_readb(_dp->aux,
> +DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, _min) != 1) {
> + DRM_DEBUG_KMS("Failed to read pwmgen bit count cap min\n");
> + return;
> + }
> + if (drm_dp_dpcd_readb(_dp->aux,
> +DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, _max) != 1) {
> + DRM_DEBUG_KMS("Failed to read pwmgen bit count cap max\n");
> + return;
> + }
> + pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> + pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> +
> + f = fxp >> pn_min;
> +
> + for (pn = pn_min; pn < pn_max && f > 255; pn++)
> + f >>= 1;
> +
> + f = clamp(f, 1, 255);
> +
> + if (drm_dp_dpcd_writeb(_dp->aux,
> +DP_EDP_PWMGEN_BIT_COUNT, pn) < 0) {
> + DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n");
> + return;
> + }
> + if (drm_dp_dpcd_writeb(_dp->aux,
> +DP_EDP_BACKLIGHT_FREQ_SET, (u8) f) < 0) {
> + DRM_DEBUG_KMS("Failed to write aux backlight freq\n");
> + return;
> + }
> +}
> +
>  static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
>  {
>   struct intel_dp *intel_dp = enc_to_intel_dp(>encoder->base);
>   uint8_t dpcd_buf = 0;
>   uint8_t new_dpcd_buf = 0;
>   uint8_t edp_backlight_mode = 0;
> + bool freq_cap;
>  
>   if (drm_dp_dpcd_readb(_dp->aux,
>   DP_EDP_BACKLIGHT_MODE_SET_REGISTER, _buf) != 1) {
> @@ -150,6 +214,10 @@ static void intel_dp_aux_enable_backlight(struct 
> intel_connector *connector)
>   DRM_DEBUG_KMS("Enable dynamic brightness.\n");
>   }
>  
> + freq_cap = intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP;
> + if (freq_cap)
> + new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
> +
>   if (new_dpcd_buf != dpcd_buf) {
>   if (drm_dp_dpcd_writeb(_dp->aux,
>   DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf) < 0) {
> @@ -157,6 +225,9 @@ static void intel_dp_aux_enable_backlight(struct 
> intel_connector *connector)
>   }
>   }
>  
> + if (freq_cap)
> + intel_dp_aux_set_pwm_freq(connector);
> +
>   set_aux_backlight_enable(intel_dp, true);
>   intel_dp_aux_set_backlight(connector, connector->panel.backlight.level);
>  }

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[Intel-gfx] [PATCH v5 9/9] drm/i915: Set PWM divider to match desired frequency in vbt

2017-05-03 Thread Puthikorn Voravootivat 
Read desired PWM frequency from panel vbt and calculate the
value for divider in DPCD address 0x724 and 0x728 to match
that frequency as close as possible.

Signed-off-by: Puthikorn Voravootivat 
---
 drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 71 +++
 1 file changed, 71 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c 
b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
index fc26fea94fd4..441ad434a82b 100644
--- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
@@ -113,12 +113,76 @@ intel_dp_aux_set_dynamic_backlight_percent(struct 
intel_dp *intel_dp,
}
 }
 
+/*
+ * Set PWM Frequency divider to match desired frequency in vbt.
+ * The PWM Frequency is calculated as 27Mhz / (F x P).
+ * - Where F = PWM Frequency Pre-Divider value programmed by field 7:0 of the
+ * EDP_BACKLIGHT_FREQ_SET register (DPCD Address 00728h)
+ * - Where P = 2^Pn, where Pn is the value programmed by field 4:0 of the
+ * EDP_PWMGEN_BIT_COUNT register (DPCD Address 00724h)
+ */
+static void intel_dp_aux_set_pwm_freq(struct intel_connector *connector)
+{
+   struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
+   struct intel_dp *intel_dp = enc_to_intel_dp(>encoder->base);
+   int freq, fxp, f;
+   u8 pn, pn_min, pn_max;
+
+   /* Find desired value of (F x P)
+* Note that, if F x P is out of supported range, the maximum value or
+* minimum value will applied automatically. So no need to check that.
+*/
+   freq = dev_priv->vbt.backlight.pwm_freq_hz;
+   DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz\n", freq);
+   if (!freq) {
+   DRM_DEBUG_KMS("Use panel default backlight frequency\n");
+   return;
+   }
+
+   fxp = DP_EDP_BACKLIGHT_FREQ_BASE / freq;
+
+   /* Use lowest possible value of Pn to try to make F to be between 1 and
+* 255 while still in the range Pn_min and Pn_max
+*/
+   if (drm_dp_dpcd_readb(_dp->aux,
+  DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, _min) != 1) {
+   DRM_DEBUG_KMS("Failed to read pwmgen bit count cap min\n");
+   return;
+   }
+   if (drm_dp_dpcd_readb(_dp->aux,
+  DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, _max) != 1) {
+   DRM_DEBUG_KMS("Failed to read pwmgen bit count cap max\n");
+   return;
+   }
+   pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+   pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+
+   f = fxp >> pn_min;
+
+   for (pn = pn_min; pn < pn_max && f > 255; pn++)
+   f >>= 1;
+
+   f = clamp(f, 1, 255);
+
+   if (drm_dp_dpcd_writeb(_dp->aux,
+  DP_EDP_PWMGEN_BIT_COUNT, pn) < 0) {
+   DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n");
+   return;
+   }
+   if (drm_dp_dpcd_writeb(_dp->aux,
+  DP_EDP_BACKLIGHT_FREQ_SET, (u8) f) < 0) {
+   DRM_DEBUG_KMS("Failed to write aux backlight freq\n");
+   return;
+   }
+}
+
 static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
 {
struct intel_dp *intel_dp = enc_to_intel_dp(>encoder->base);
uint8_t dpcd_buf = 0;
uint8_t new_dpcd_buf = 0;
uint8_t edp_backlight_mode = 0;
+   bool freq_cap;
 
if (drm_dp_dpcd_readb(_dp->aux,
DP_EDP_BACKLIGHT_MODE_SET_REGISTER, _buf) != 1) {
@@ -150,6 +214,10 @@ static void intel_dp_aux_enable_backlight(struct 
intel_connector *connector)
DRM_DEBUG_KMS("Enable dynamic brightness.\n");
}
 
+   freq_cap = intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP;
+   if (freq_cap)
+   new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
+
if (new_dpcd_buf != dpcd_buf) {
if (drm_dp_dpcd_writeb(_dp->aux,
DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf) < 0) {
@@ -157,6 +225,9 @@ static void intel_dp_aux_enable_backlight(struct 
intel_connector *connector)
}
}
 
+   if (freq_cap)
+   intel_dp_aux_set_pwm_freq(connector);
+
set_aux_backlight_enable(intel_dp, true);
intel_dp_aux_set_backlight(connector, connector->panel.backlight.level);
 }
-- 
2.13.0.rc1.294.g07d810a77f-goog

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