On Tue, 24 Aug 2021, Lee Shawn C <shawn.c.lee@xxxxxxxxx> wrote:
> So far, DCS backlight driver hardcode (0xFF) for max brightness level.
> MIPI DCS spec allow max 0xFFFF for set_display_brightness (51h) command.
> And VBT brightness precision bits can support 8 ~ 16 bits.
>
> We should set correct precision bits in VBT that meet panel's request.
> Driver can refer to this setting then configure max brightness level
> in DCS backlight driver properly.
>
> v2: modify variable name brightness_precision_bits instead of
> max_brightness_level.
>
> Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Cc: Vandita Kulkarni <vandita.kulkarni@xxxxxxxxx>
> Cc: Cooper Chiou <cooper.chiou@xxxxxxxxx>
> Cc: William Tseng <william.tseng@xxxxxxxxx>
> Signed-off-by: Lee Shawn C <shawn.c.lee@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_bios.c | 3 +++
> drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c | 8 ++++++--
> drivers/gpu/drm/i915/i915_drv.h | 1 +
> 3 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index e86e6ed2d3bf..ccaf0a3100f7 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -483,6 +483,9 @@ parse_lfp_backlight(struct drm_i915_private *i915,
> level = 255;
> }
> i915->vbt.backlight.min_brightness = min_level;
> +
> + i915->vbt.backlight.brightness_precision_bits =
> + backlight_data->brightness_precision_bits[panel_type];
> } else {
> level = backlight_data->level[panel_type];
> i915->vbt.backlight.min_brightness = entry->min_brightness;
> diff --git a/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c b/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
> index 584c14c4cbd0..21ab9e1acb57 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsi_dcs_backlight.c
> @@ -147,10 +147,14 @@ static void dcs_enable_backlight(const struct intel_crtc_state *crtc_state,
> static int dcs_setup_backlight(struct intel_connector *connector,
> enum pipe unused)
> {
> + struct drm_device *dev = connector->base.dev;
> + struct drm_i915_private *dev_priv = to_i915(dev);
> struct intel_panel *panel = &connector->panel;
>
> - panel->backlight.max = PANEL_PWM_MAX_VALUE;
> - panel->backlight.level = PANEL_PWM_MAX_VALUE;
> + panel->backlight.max = (dev_priv->vbt.backlight.brightness_precision_bits > 8) \
> + ? (1 << dev_priv->vbt.backlight.brightness_precision_bits) - 1 \
> + : PANEL_PWM_MAX_VALUE;
> + panel->backlight.level = panel->backlight.max;
If the precision is < 8, why would max be 0xff? Use GENMASK() perhaps?
BR,
Jani.
>
> return 0;
> }
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 005b1cec7007..1b42e39a7cd4 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -706,6 +706,7 @@ struct intel_vbt_data {
>
> struct {
> u16 pwm_freq_hz;
> + u16 brightness_precision_bits;
> bool present;
> bool active_low_pwm;
> u8 min_brightness; /* min_brightness/255 of max */
--
Jani Nikula, Intel Open Source Graphics Center
