Re: [Intel-gfx] [PATCH v2 1/3] drm/i915/vbt: Fix backlight parsing for VBT 234+

["Souza, Jose" <jose.souza@intel.com>]

On Tue, 2020-10-06 at 12:04 +0300, Jani Nikula wrote:
> On Tue, 29 Sep 2020, José Roberto de Souza <jose.souza@intel.com> wrote:
> > Child min_brightness is obsolete from VBT 234+, instead the new
> > min_brightness field in the main structure should be used.
> > 
> > This new field is 16 bits wide, so backlight_precision_bits is needed
> > to check if value needs to be scaled down but it is only available in
> > VBT 236+ so working around it by using the also new backlight_level
> > in the main struct.
> > 
> > v2:
> > - missed that backlight_data->level is also obsolete
> > 
> > BSpec: 20149
> > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_bios.c     | 30 +++++++++++++++++--
> >  drivers/gpu/drm/i915/display/intel_vbt_defs.h | 12 ++++++--
> >  2 files changed, 38 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> > index 4716484af62d..58e5657a77bb 100644
> > --- a/drivers/gpu/drm/i915/display/intel_bios.c
> > +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> > @@ -425,6 +425,7 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv,
> >  	const struct bdb_lfp_backlight_data *backlight_data;
> >  	const struct lfp_backlight_data_entry *entry;
> >  	int panel_type = dev_priv->vbt.panel_type;
> > +	u16 level;
> >  
> > 
> > 
> > 
> >  	backlight_data = find_section(bdb, BDB_LVDS_BACKLIGHT);
> >  	if (!backlight_data)
> > @@ -459,14 +460,39 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv,
> >  
> > 
> > 
> > 
> >  	dev_priv->vbt.backlight.pwm_freq_hz = entry->pwm_freq_hz;
> >  	dev_priv->vbt.backlight.active_low_pwm = entry->active_low_pwm;
> > -	dev_priv->vbt.backlight.min_brightness = entry->min_brightness;
> > +
> > +	if (bdb->version >= 234) {
> > +		bool scale = false;
> > +		u16 min_level;
> > +
> > +		level = backlight_data->backlight_level[panel_type].level;
> > +		min_level = backlight_data->backlight_min_level[panel_type].level;
> > +
> > +		if (bdb->version >= 236)
> > +			scale = backlight_data->backlight_precision_bits[panel_type] == 16;
> > +		else
> > +			scale = level > 255;
> > +
> > +		if (scale)
> > +			min_level = min_level / 255;
> > +
> > +		if (min_level > 255) {
> > +			drm_warn(&dev_priv->drm, "Backlight min level > 255\n");
> > +			level = 255;
> > +		}
> > +		dev_priv->vbt.backlight.min_brightness = min_level;
> > +	} else {
> > +		level = backlight_data->level[panel_type];
> > +		dev_priv->vbt.backlight.min_brightness = entry->min_brightness;
> > +	}
> > +
> >  	drm_dbg_kms(&dev_priv->drm,
> >  		    "VBT backlight PWM modulation frequency %u Hz, "
> >  		    "active %s, min brightness %u, level %u, controller %u\n",
> >  		    dev_priv->vbt.backlight.pwm_freq_hz,
> >  		    dev_priv->vbt.backlight.active_low_pwm ? "low" : "high",
> >  		    dev_priv->vbt.backlight.min_brightness,
> > -		    backlight_data->level[panel_type],
> > +		    level,
> >  		    dev_priv->vbt.backlight.controller);
> >  }
> >  
> > 
> > 
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_vbt_defs.h b/drivers/gpu/drm/i915/display/intel_vbt_defs.h
> > index 54bcc6a6947c..b4742c4fde97 100644
> > --- a/drivers/gpu/drm/i915/display/intel_vbt_defs.h
> > +++ b/drivers/gpu/drm/i915/display/intel_vbt_defs.h
> > @@ -782,7 +782,7 @@ struct lfp_backlight_data_entry {
> >  	u8 active_low_pwm:1;
> >  	u8 obsolete1:5;
> >  	u16 pwm_freq_hz;
> > -	u8 min_brightness;
> > +	u8 min_brightness; /* Obsolete from 234+ */
> >  	u8 obsolete2;
> >  	u8 obsolete3;
> >  } __packed;
> > @@ -792,11 +792,19 @@ struct lfp_backlight_control_method {
> >  	u8 controller:4;
> >  } __packed;
> >  
> > 
> > 
> > 
> > +struct lfp_backlight_level {
> > +	u32 level : 16;
> > +	u32 reserved : 16;
> 
> That looks like two u16's to me. ;)

Okay, anything else to be changed in the next version?

> 
> BR,
> Jani.
> 
> 
> > +} __packed;
> > +
> >  struct bdb_lfp_backlight_data {
> >  	u8 entry_size;
> >  	struct lfp_backlight_data_entry data[16];
> > -	u8 level[16];
> > +	u8 level[16]; /* Obsolete from 234+ */
> >  	struct lfp_backlight_control_method backlight_control[16];
> > +	struct lfp_backlight_level backlight_level[16];		/* 234+ */
> > +	struct lfp_backlight_level backlight_min_level[16];	/* 234+ */
> > +	u8 backlight_precision_bits[16];					/* 236+ */
> >  } __packed;
> >  
> > 
> > 
> > 
> >  /*
> 

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