[alsa-devel] [PATCH 2/5] ALSA: hda: Add api to program stripe control bits

[Sameer Pujar]

Controllers and codecs can support striping of audio out across
multiple SDO lines. The number of supported SDO lines can be
specific to chip. GCAP register can be read to know the maximum
supported SDO lines.

snd_hdac_get_stream_stripe_ctl() is exposed to program stripe bits
on controller and codec side.
stripe value: 0 for 1SDO, 1 for 2SDO, 2 for 4SDO lines, etc.,

Signed-off-by: Sameer Pujar <spujar at nvidia.com>
Reviewed-by: Mohan Kumar D <mkumard at nvidia.com>
Reviewed-by: Ravindra Lokhande <rlokhande at nvidia.com>
---
 include/sound/hdaudio.h |  3 +++
 sound/hda/hdac_stream.c | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/include/sound/hdaudio.h b/include/sound/hdaudio.h
index b4fa1c7..45f944d 100644
--- a/include/sound/hdaudio.h
+++ b/include/sound/hdaudio.h
@@ -539,6 +539,9 @@ void snd_hdac_stream_sync(struct hdac_stream *azx_dev, bool start,
 			  unsigned int streams);
 void snd_hdac_stream_timecounter_init(struct hdac_stream *azx_dev,
 				      unsigned int streams);
+int snd_hdac_get_stream_stripe_ctl(struct hdac_bus *bus,
+				struct snd_pcm_substream *substream);
+
 /*
  * macros for easy use
  */
diff --git a/sound/hda/hdac_stream.c b/sound/hda/hdac_stream.c
index eee4223..b403b05 100644
--- a/sound/hda/hdac_stream.c
+++ b/sound/hda/hdac_stream.c
@@ -13,6 +13,40 @@
 #include "trace.h"
 
 /**
+ * snd_hdac_get_stream_stripe_ctl - get stripe control value
+ * @bus: HD-audio core bus
+ * @substream: PCM substream
+ */
+int snd_hdac_get_stream_stripe_ctl(struct hdac_bus *bus,
+				   struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	unsigned int channels = runtime->channels,
+		     rate = runtime->rate,
+		     bits_per_sample = runtime->sample_bits,
+		     max_sdo_lines, value, sdo_line;
+
+	/* T_AZA_GCAP_NSDO is 1:2 bitfields in GCAP */
+	max_sdo_lines = snd_hdac_chip_readl(bus, GCAP) & AZX_GCAP_NSDO;
+
+	/* following is from HD audio spec */
+	for (sdo_line = max_sdo_lines; sdo_line > 0; sdo_line >>= 1) {
+		if (rate > 48000)
+			value = (channels * bits_per_sample *
+					(rate / 48000)) / sdo_line;
+		else
+			value = channels * bits_per_sample / sdo_line;
+
+		if (value >= 8)
+			break;
+	}
+
+	/* stripe value: 0 for 1SDO, 1 for 2SDO, 2 for 4SDO lines */
+	return sdo_line >> 1;
+}
+EXPORT_SYMBOL_GPL(snd_hdac_get_stream_stripe_ctl);
+
+/**
  * snd_hdac_stream_init - initialize each stream (aka device)
  * @bus: HD-audio core bus
  * @azx_dev: HD-audio core stream object to initialize
-- 
2.7.4


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