linux-kernel - Re: [PATCH v3] drm/dp: add an API to indicate if sink supports VSC SDP

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Message-ID: <87il2u9ei9.fsf@intel.com>
Date: Mon, 12 Feb 2024 12:13:34 +0200
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>,
 dri-devel@...ts.freedesktop.org, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>
Cc: Paloma Arellano <quic_parellan@...cinc.com>, robdclark@...il.com,
 freedreno@...ts.freedesktop.org, dmitry.baryshkov@...aro.org,
 intel-gfx@...ts.freedesktop.org, ville.syrjala@...ux.intel.com,
 quic_jesszhan@...cinc.com, Abhinav Kumar <quic_abhinavk@...cinc.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] drm/dp: add an API to indicate if sink supports VSC SDP

On Sat, 10 Feb 2024, Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
> From: Paloma Arellano <quic_parellan@...cinc.com>
>
> YUV420 format is supported only in the VSC SDP packet and not through
> MSA. Hence add an API which indicates the sink support which can be used
> by the rest of the DP programming.
>
> changes in v3:
> 	- fix the commit title prefix to drm/dp
> 	- get rid of redundant !!
> 	- break out this change from series [1] to get acks from drm core
> 	  maintainers
>
> Changes in v2:
> 	- Move VSC SDP support check API from dp_panel.c to
> 	  drm_dp_helper.c
>
> [1]: https://patchwork.freedesktop.org/series/129180/
>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Paloma Arellano <quic_parellan@...cinc.com>
> Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
> ---
>  drivers/gpu/drm/display/drm_dp_helper.c | 21 +++++++++++++++++++++
>  include/drm/display/drm_dp_helper.h     |  1 +
>  2 files changed, 22 insertions(+)
>
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> index b1ca3a1100da..7a851f92b249 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -2916,6 +2916,27 @@ void drm_dp_vsc_sdp_log(const char *level, struct device *dev,
>  }
>  EXPORT_SYMBOL(drm_dp_vsc_sdp_log);
>  
> +/**
> + * drm_dp_vsc_sdp_supported() - check if vsc sdp is supported
> + * @aux: DisplayPort AUX channel
> + * @dpcd: DisplayPort configuration data
> + *
> + * Returns true if vsc sdp is supported, else returns false
> + */
> +bool drm_dp_vsc_sdp_supported(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE])
> +{
> +	u8 rx_feature;
> +
> +	if (drm_dp_dpcd_readb(aux, DP_DPRX_FEATURE_ENUMERATION_LIST, &rx_feature) != 1) {
> +		drm_dbg_dp(aux->drm_dev, "failed to read DP_DPRX_FEATURE_ENUMERATION_LIST\n");
> +		return false;
> +	}
> +
> +	return (dpcd[DP_DPCD_REV] >= DP_DPCD_REV_13) &&
> +		(rx_feature & DP_VSC_SDP_EXT_FOR_COLORIMETRY_SUPPORTED);

I guess you could bail out early without further dpcd access with the
dpcd rev check?

BR,
Jani.


> +}
> +EXPORT_SYMBOL(drm_dp_vsc_sdp_supported);
> +
>  /**
>   * drm_dp_get_pcon_max_frl_bw() - maximum frl supported by PCON
>   * @dpcd: DisplayPort configuration data
> diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> index 863b2e7add29..948381b2b0b1 100644
> --- a/include/drm/display/drm_dp_helper.h
> +++ b/include/drm/display/drm_dp_helper.h
> @@ -100,6 +100,7 @@ struct drm_dp_vsc_sdp {
>  
>  void drm_dp_vsc_sdp_log(const char *level, struct device *dev,
>  			const struct drm_dp_vsc_sdp *vsc);
> +bool drm_dp_vsc_sdp_supported(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE]);
>  
>  int drm_dp_psr_setup_time(const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE]);

-- 
Jani Nikula, Intel