[Intel-gfx] [RFC 3/3] drm/i915/display: Add wrapper to Compute SAD

[Borah, Chaitanya Kumar]

Hello Mitul,

> -----Original Message-----
> From: Golani, Mitulkumar Ajitkumar <mitulkumar.ajitkumar.golani at intel.com>
> Sent: Friday, June 9, 2023 11:12 PM
> To: intel-gfx at lists.freedesktop.org
> Cc: Shankar, Uma <uma.shankar at intel.com>; Borah, Chaitanya Kumar
> <chaitanya.kumar.borah at intel.com>; Golani, Mitulkumar Ajitkumar
> <mitulkumar.ajitkumar.golani at intel.com>; Nautiyal, Ankit K
> <ankit.k.nautiyal at intel.com>
> Subject: [RFC 3/3] drm/i915/display: Add wrapper to Compute SAD
> 
> Compute SADs that takes into account the supported rate and channel based
> on the capabilities of the audio source. This wrapper function should
> encapsulate the logic for determining the supported rate and channel and
> should return a set of SADs that are compatible with the source.
> 
> --v1:
> - call intel_audio_compute_eld in this commit as it is defined here
> 
> Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_audio.c | 66 ++++++++++++++++++++++
> drivers/gpu/drm/i915/display/intel_audio.h |  1 +
> drivers/gpu/drm/i915/display/intel_hdmi.c  |  2 +
>  3 files changed, 69 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_audio.c
> b/drivers/gpu/drm/i915/display/intel_audio.c
> index e20ffc8e9654..a6a58b0f0717 100644
> --- a/drivers/gpu/drm/i915/display/intel_audio.c
> +++ b/drivers/gpu/drm/i915/display/intel_audio.c
> @@ -794,6 +794,72 @@ bool intel_audio_compute_config(struct
> intel_encoder *encoder,
>  	return true;
>  }
> 
> +static unsigned int drm_sad_to_channels(const u8 *sad) {
> +	return 1 + (sad[0] & 0x7);
> +}
> +

We can do away with the drm_ prefix here.

> +static inline u8 *parse_sad(u8 *eld)
> +{

Nit: eld_to_sad() could be a better name here.

> +	unsigned int ver, mnl;
> +
> +	ver = (eld[DRM_ELD_VER] & DRM_ELD_VER_MASK) >>
> DRM_ELD_VER_SHIFT;
> +	if (ver != 2 && ver != 31)
> +		return NULL;
> +
> +	mnl = drm_eld_mnl(eld);
> +	if (mnl > 16)
> +		return NULL;
> +
> +	return eld + DRM_ELD_CEA_SAD(mnl, 0);
> +}
> +
> +static u8 get_supported_freq_mask(struct intel_crtc_state *crtc_state)
> +{
> +	int audio_freq_hz[] = {32000, 44100, 48000, 88000, 96000, 176000,
> 192000, 0};

Please check if we really need this trailing 0 here.

To cover the case where the maximum rate is set to 0Hz(init value) we can have a check of 

if (crtc_state->audio.max_frequency < 32000)


Regards

Chaitanya

> +	u8 mask = 0;
> +
> +	for (u8 index = 0; index < ARRAY_SIZE(audio_freq_hz); index++) {
> +		mask |= 1 << index;
> +		if (crtc_state->audio.max_frequency != audio_freq_hz[index])
> +			continue;
> +		else
> +			break;
> +	}
> +
> +	return mask;
> +}
> +
> +void intel_audio_compute_eld(struct intel_crtc_state *crtc_state) {
> +	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
> +	u8 *eld, *sad, index, mask = 0;
> +
> +	eld = crtc_state->eld;
> +	if (!eld) {
> +		drm_err(&i915->drm, "failed to locate eld\n");
> +		return;
> +	}
> +
> +	sad = (u8 *)parse_sad(eld);
> +	if (sad) {
> +		mask = get_supported_freq_mask(crtc_state);
> +
> +		for (index = 0; index < drm_eld_sad_count(eld); index++, sad
> += 3) {
> +			/*
> +			 *  Respect to source restrictions. If source limit is
> greater than sink
> +			 *  capabilities then follow to sink's highest supported
> rate.
> +			 */
> +			if (drm_sad_to_channels(sad) >= crtc_state-
> >audio.max_channel) {
> +				sad[0] &= ~0x7;
> +				sad[0] |= crtc_state->audio.max_channel - 1;
> +			}
> +
> +			sad[1] &= mask;
> +		}
> +	}
> +}
> +
>  /**
>   * intel_audio_codec_enable - Enable the audio codec for HD audio
>   * @encoder: encoder on which to enable audio diff --git
> a/drivers/gpu/drm/i915/display/intel_audio.h
> b/drivers/gpu/drm/i915/display/intel_audio.h
> index 07d034a981e9..2ec7fafd9711 100644
> --- a/drivers/gpu/drm/i915/display/intel_audio.h
> +++ b/drivers/gpu/drm/i915/display/intel_audio.h
> @@ -14,6 +14,7 @@ struct intel_crtc_state;  struct intel_encoder;
> 
>  void intel_audio_hooks_init(struct drm_i915_private *dev_priv);
> +void intel_audio_compute_eld(struct intel_crtc_state *crtc_state);
>  bool intel_audio_compute_config(struct intel_encoder *encoder,
>  				struct intel_crtc_state *crtc_state,
>  				struct drm_connector_state *conn_state); diff
> --git a/drivers/gpu/drm/i915/display/intel_hdmi.c
> b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index 0188a600f9f5..beafeff494f8 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -2403,6 +2403,8 @@ int intel_hdmi_compute_config(struct intel_encoder
> *encoder,
>  		return -EINVAL;
>  	}
> 
> +	intel_audio_compute_eld(pipe_config);
> +
>  	return 0;
>  }
> 
> --
> 2.25.1