[alsa-devel] [PATCH] ASoC: Intel: hdac_hdmi: Add sampling frequencies constraint

[Yong Zhi]

Playback of 44.1Khz contents with HDMI plugged returns
"Invalid pipe config".

This patch adds rate constraint to allow user space SRC
to do the converting.

Signed-off-by: Yong Zhi <yong.zhi at intel.com>
---
 sound/soc/codecs/hdac_hdmi.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/sound/soc/codecs/hdac_hdmi.c b/sound/soc/codecs/hdac_hdmi.c
index 7b8533abf637..b222a2e91463 100644
--- a/sound/soc/codecs/hdac_hdmi.c
+++ b/sound/soc/codecs/hdac_hdmi.c
@@ -288,6 +288,38 @@ static unsigned int sad_sample_bits_lpcm(const u8 *sad)
 	return (sad[2] & 7);
 }
 
+/**
+ * sad_sample_rates_lpcm - Find supported sampling frequencies
+ *
+ * @sad: pointer to CEA_SADs entry byte 2 which details sampling frequencies
+ *	 supported according to CEA-861 EDID V3. In little endian byte order.
+ *
+ *	 bit 7: Reserved (0)
+ *	 bit 6: 192kHz
+ *	 bit 5: 176kHz
+ *	 bit 4: 96kHz
+ *	 bit 3: 88kHz
+ *	 bit 2: 48kHz
+ *	 bit 1: 44kHz
+ *	 bit 0: 32kHz
+ *
+ * Return: bitmask of supported sampling frequencies.
+ */
+static u8 sad_sample_rates_lpcm(const u8 *sad)
+{
+	return (sad[1] & 0x7F);
+}
+
+static const unsigned int cea_sampling_freqs[7] = {
+	SNDRV_PCM_RATE_32000,	/* 0:  32000Hz */
+	SNDRV_PCM_RATE_44100,	/* 1:  44100Hz */
+	SNDRV_PCM_RATE_48000,	/* 2:  48000Hz */
+	SNDRV_PCM_RATE_88200,	/* 3:  88200Hz */
+	SNDRV_PCM_RATE_96000,	/* 4:  96000Hz */
+	SNDRV_PCM_RATE_176400,	/* 5: 176400Hz */
+	SNDRV_PCM_RATE_192000,	/* 6: 192000Hz */
+};
+
 static int hdac_hdmi_eld_limit_formats(struct snd_pcm_runtime *runtime,
 						void *eld)
 {
@@ -301,6 +333,8 @@ static int hdac_hdmi_eld_limit_formats(struct snd_pcm_runtime *runtime,
 
 	for (i = drm_eld_sad_count(eld_buf); i > 0; i--, sad += 3) {
 		if (sad_format(sad) == 1) { /* AUDIO_CODING_TYPE_LPCM */
+			unsigned int rates = 0;
+			u8 sad_rates, j;
 
 			/*
 			 * the controller support 20 and 24 bits in 32 bit
@@ -308,6 +342,16 @@ static int hdac_hdmi_eld_limit_formats(struct snd_pcm_runtime *runtime,
 			 */
 			if (sad_sample_bits_lpcm(sad) & 0x6)
 				formats |= SNDRV_PCM_FMTBIT_S32;
+
+			sad_rates = sad_sample_rates_lpcm(sad);
+			/* Filter out 44.1, 88.2 and 176.4Khz */
+			for (j = 0; j < 7; j += 2)
+				if (sad_rates & BIT(j))
+					rates |= cea_sampling_freqs[j];
+
+			snd_pcm_hw_constraint_mask64(runtime,
+						     SNDRV_PCM_HW_PARAM_RATE,
+						     rates);
 		}
 	}
 
-- 
2.7.4