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

[Jani Nikula]

On Tue, 29 Sep 2020, José Roberto de Souza <jose.souza at 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 Child min_brightness is obsolete from VBT 234+, instead the new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 at 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. ;)

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;
>  
>  /*

-- 
Jani Nikula, Intel Open Source Graphics Center