[PATCH 4/5] drm/i915/display: Add wrapper to Compute SAD

[Mitul Golani]

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.

Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani at intel.com>
---
 drivers/gpu/drm/i915/display/intel_audio.c | 61 ++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_audio.c b/drivers/gpu/drm/i915/display/intel_audio.c
index b4a0dae65cbf..7086c6cd7de3 100644
--- a/drivers/gpu/drm/i915/display/intel_audio.c
+++ b/drivers/gpu/drm/i915/display/intel_audio.c
@@ -794,6 +794,67 @@ bool intel_audio_compute_config(struct intel_encoder *encoder,
 	return true;
 }
 
+static inline u8 *parse_sad(u8 *eld)
+{
+	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);
+}
+
+u8 get_supported_freq_mask(struct intel_crtc_state *crtc_state)
+{
+	int audio_freq_hz[] = {32000, 44100, 48000, 88000, 96000, 176000, 192000, 0};
+	u8 mask = 0;
+
+	for (u8 index = 0; index < ARRAY_SIZE(audio_freq_hz); index++) {
+		mask |= 1 << index;
+		if (crtc_state->audio_config.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_config.max_channel) {
+				sad[0] &= ~DRM_ELD_SAD_CHANNELS_MASK;
+				sad[0] |= crtc_state->audio_config.max_channel - 1;
+			}
+
+			sad[1] &= mask;
+		}
+	}
+}
+
 /**
  * intel_audio_codec_enable - Enable the audio codec for HD audio
  * @encoder: encoder on which to enable audio
-- 
2.25.1