Re: [6/7] drm/i915/dp: Write panel override luminance values

[Sebastian Wick <sebastian.wick@redhat.com>]

On Thu, Apr 04, 2024 at 08:59:30AM +0530, Suraj Kandpal wrote:
> Write panel override luminance values which helps the TCON decide
> if tone mapping needs to be enabled or not.
> 
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
> ---
>  .../drm/i915/display/intel_dp_aux_backlight.c | 25 +++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> index 7af876e2d210..20dd5a6a0f3f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -381,6 +381,29 @@ static const char *dpcd_vs_pwm_str(bool aux)
>  	return aux ? "DPCD" : "PWM";
>  }
>  
> +static void
> +intel_dp_aux_write_panel_luminance_override(struct intel_connector *connector)
> +{
> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> +	struct intel_panel *panel = &connector->panel;
> +	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
> +	int ret;
> +	u8 buf[4] = {};
> +
> +	buf[0] = panel->backlight.min & 0xFF;
> +	buf[1] = (panel->backlight.min & 0xFF00) >> 8;
> +	buf[2] = panel->backlight.max & 0xFF;
> +	buf[3] = (panel->backlight.max & 0xFF00) >> 8;
> +
> +	ret = drm_dp_dpcd_write(&intel_dp->aux,
> +				INTEL_EDP_HDR_PANEL_LUMINANCE_OVERRIDE,
> +				buf, sizeof(buf));
> +	if (ret < 0)
> +		drm_dbg_kms(&i915->drm,
> +			    "Panel Luminance DPCD reg write failed, err:-%d\n",
> +			    ret);
> +}
> +
>  static int
>  intel_dp_aux_hdr_setup_backlight(struct intel_connector *connector, enum pipe pipe)
>  {
> @@ -412,6 +435,8 @@ intel_dp_aux_hdr_setup_backlight(struct intel_connector *connector, enum pipe pi
>  		panel->backlight.min = 0;
>  	}
>  
> +	intel_dp_aux_write_panel_luminance_override(connector);
> +

Should this really always be set? It says override. Doesn't the TCON
have some values already that we're overriding?

>  	drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] Using AUX HDR interface for backlight control (range %d..%d)\n",
>  		    connector->base.base.id, connector->base.name,
>  		    panel->backlight.min, panel->backlight.max);