On Tue, 2022-04-12 at 08:25 +0300, Jouni Högander wrote:
> We have now seen panel (XMG Core 15 e21 laptop) avertizing 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
> does detection from DPCD registers only if this data block exists.
>
> 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@xxxxxxxxxx>
> Cc: Mika Kahola <mika.kahola@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
> Tested-by: Filippo Falezza <filippo.falezza@xxxxxxxxxx>
> Signed-off-by: Jouni Högander <jouni.hogander@xxxxxxxxx>
> ---
> .../gpu/drm/i915/display/intel_dp_aux_backlight.c | 13 +++++++++++++
> 1 file changed, 13 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 97cf3cac0105..f69e185b58c1 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -108,6 +108,19 @@ intel_dp_aux_supports_hdr_backlight(struct
> intel_connector *connector)
> int ret;
> u8 tcon_cap[4];
>
> + /*
> + * 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 (!(connector->base.hdr_sink_metadata.hdmi_type1.metadata_type &
> + BIT(HDMI_STATIC_METADATA_TYPE1)))
> + return false;
The block used for this is actually for HDMI?? How bizarre…
Anyway yeah - patch looks good to me, but I think we should print a debugging
message of some sort when we determine that there's no HDR backlight because
of the EDID - along with printing instructions for how the user can override
it if we've made the wrong choice along with reporting a bug. Also - we should
have the
Cc: stable@xxxxxxxxxxxxxxx
tag from dim added here using `dim fixes $commit`.
With that fixed:
Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
> +
> intel_dp_wait_source_oui(intel_dp);
>
> ret = drm_dp_dpcd_read(aux, INTEL_EDP_HDR_TCON_CAP0, tcon_cap,
> sizeof(tcon_cap));
--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat
