[Intel-gfx] [PATCH v2] drm/i915: Check EDID for HDR static metadata when choosing blc

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude at redhat.com>

On Wed, 2022-04-13 at 11:28 +0300, Jouni Högander wrote:
> We have now seen panel (XMG Core 15 e21 laptop) advertizing support
> for Intel proprietary eDP backlight control via DPCD registers, but
> actually working only with legacy pwm control.
> 
> This patch adds panel EDID check for possible HDR static metadata and
> Intel proprietary eDP backlight control is used only if that exists.
> Missing HDR static metadata is ignored if user specifically asks for
> Intel proprietary eDP backlight control via enable_dpcd_backlight
> parameter.
> 
> v2 :
> - Ignore missing HDR static metadata if Intel proprietary eDP
>   backlight control is forced via i915.enable_dpcd_backlight
> - Printout info message if panel is missing HDR static metadata and
>   support for Intel proprietary eDP backlight control is detected
> 
> Fixes: 4a8d79901d5b ("drm/i915/dp: Enable Intel's HDR backlight interface
> (only SDR for now)")
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5284
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: Mika Kahola <mika.kahola at intel.com>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Cc: Filippo Falezza <filippo.falezza at outlook.it>
> Cc: stable at vger.kernel.org
> Signed-off-by: Jouni Högander <jouni.hogander at intel.com>
> ---
>  .../drm/i915/display/intel_dp_aux_backlight.c | 34 ++++++++++++++-----
>  1 file changed, 26 insertions(+), 8 deletions(-)
> 
> 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 97cf3cac0105..fb6cf30ee628 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -97,6 +97,14 @@
>  
>  #define INTEL_EDP_BRIGHTNESS_OPTIMIZATION_1                           
> 0x359
>  
> +enum intel_dp_aux_backlight_modparam {
> +       INTEL_DP_AUX_BACKLIGHT_AUTO = -1,
> +       INTEL_DP_AUX_BACKLIGHT_OFF = 0,
> +       INTEL_DP_AUX_BACKLIGHT_ON = 1,
> +       INTEL_DP_AUX_BACKLIGHT_FORCE_VESA = 2,
> +       INTEL_DP_AUX_BACKLIGHT_FORCE_INTEL = 3,
> +};
> +
>  /* Intel EDP backlight callbacks */
>  static bool
>  intel_dp_aux_supports_hdr_backlight(struct intel_connector *connector)
> @@ -126,6 +134,24 @@ intel_dp_aux_supports_hdr_backlight(struct
> intel_connector *connector)
>                 return false;
>         }
>  
> +       /*
> +        * If we don't have HDR static metadata there is no way to
> +        * runtime detect used range for nits based control. For now
> +        * do not use Intel proprietary eDP backlight control if we
> +        * don't have this data in panel EDID. In case we find panel
> +        * which supports only nits based control, but doesn't provide
> +        * HDR static metadata we need to start maintaining table of
> +        * ranges for such panels.
> +        */
> +       if (i915->params.enable_dpcd_backlight !=
> INTEL_DP_AUX_BACKLIGHT_FORCE_INTEL &&
> +           !(connector->base.hdr_sink_metadata.hdmi_type1.metadata_type &
> +             BIT(HDMI_STATIC_METADATA_TYPE1))) {
> +               drm_info(&i915->drm,
> +                        "Panel is missing HDR static metadata. Possible
> support for Intel HDR backlight interface is not used. If your backlight
> controls don't work try booting with i915.enable_dpcd_backlight=%d. needs
> this, please file a _new_ bug report on drm/i915, see " FDO_BUG_URL " for
> details.\n",
> +                        INTEL_DP_AUX_BACKLIGHT_FORCE_INTEL);
> +               return false;
> +       }
> +
>         panel->backlight.edp.intel.sdr_uses_aux =
>                 tcon_cap[2] & INTEL_EDP_SDR_TCON_BRIGHTNESS_AUX_CAP;
>  
> @@ -413,14 +439,6 @@ static const struct intel_panel_bl_funcs
> intel_dp_vesa_bl_funcs = {
>         .get = intel_dp_aux_vesa_get_backlight,
>  };
>  
> -enum intel_dp_aux_backlight_modparam {
> -       INTEL_DP_AUX_BACKLIGHT_AUTO = -1,
> -       INTEL_DP_AUX_BACKLIGHT_OFF = 0,
> -       INTEL_DP_AUX_BACKLIGHT_ON = 1,
> -       INTEL_DP_AUX_BACKLIGHT_FORCE_VESA = 2,
> -       INTEL_DP_AUX_BACKLIGHT_FORCE_INTEL = 3,
> -};
> -
>  int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
>  {
>         struct drm_device *dev = connector->base.dev;

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat