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Commit 8d48c016 authored by Takashi Iwai's avatar Takashi Iwai
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ALSA: x86: Allow single period PCM operation 



This is an implementation of PCM streaming with only 1 period.
Since the hardware requires the refresh of BDs after each BD
processing finishes, we'd need at least two BDs.  The trick is that
both BDs point to the same content: the address of the PCM buffer
head, and the whole buffer size.  Then it loops over to the whole
buffer again after it finished once.

Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent a9ebdd0e

sound/x86/intel_hdmi_audio.c

+12 −2
Original line number Diff line number Diff line
@@ -822,6 +822,11 @@ static int had_prog_n(u32 aud_samp_freq, u32 *n_param, 
 *

 * For nperiods < 4, the remaining BDs out of 4 are marked as invalid, so that

 * the hardware skips those BDs in the loop.

 *

 * An exceptional setup is the case with nperiods=1.  Since we have to update

 * BDs after finishing one BD processing, we'd need at least two BDs, where

 * both BDs point to the same content, the same address, the same size of the

 * whole PCM buffer.

 */



#define AUD_BUF_ADDR(x)		(AUD_BUF_A_ADDR + (x) * HAD_REG_WIDTH)
@@ -864,6 +869,8 @@ static void had_init_ringbuf(struct snd_pcm_substream *substream, 


	num_periods = runtime->periods;

	intelhaddata->num_bds = min(num_periods, HAD_NUM_OF_RING_BUFS);

	/* set the minimum 2 BDs for num_periods=1 */

	intelhaddata->num_bds = max(intelhaddata->num_bds, 2U);

	intelhaddata->period_bytes =

		frames_to_bytes(runtime, runtime->period_size);

	WARN_ON(intelhaddata->period_bytes & 0x3f);
@@ -873,7 +880,7 @@ static void had_init_ringbuf(struct snd_pcm_substream *substream, 
	intelhaddata->pcmbuf_filled = 0;



	for (i = 0; i < HAD_NUM_OF_RING_BUFS; i++) {

		if (i < num_periods)

		if (i < intelhaddata->num_bds)

			had_prog_bd(substream, intelhaddata);

		else /* invalidate the rest */

			had_invalidate_bd(intelhaddata, i);
@@ -1255,7 +1262,10 @@ static snd_pcm_uframes_t had_pcm_pointer(struct snd_pcm_substream *substream) 
	len = had_process_ringbuf(substream, intelhaddata);

	if (len < 0)

		return SNDRV_PCM_POS_XRUN;

	return bytes_to_frames(substream->runtime, len);

	len = bytes_to_frames(substream->runtime, len);

	/* wrapping may happen when periods=1 */

	len %= substream->runtime->buffer_size;

	return len;

}



/*

sound/x86/intel_hdmi_lpe_audio.h

+1 −1
Original line number Diff line number Diff line
@@ -31,7 +31,7 @@ 
#define HAD_MAX_BUFFER		((1024 * 1024 - 1) & ~0x3f)

#define HAD_DEFAULT_BUFFER	(600 * 1024) /* default prealloc size */

#define HAD_MAX_PERIODS		256	/* arbitrary, but should suffice */

#define HAD_MIN_PERIODS		2

#define HAD_MIN_PERIODS		1

#define HAD_MAX_PERIOD_BYTES	((HAD_MAX_BUFFER / HAD_MIN_PERIODS) & ~0x3f)

#define HAD_MIN_PERIOD_BYTES	1024	/* might be smaller */

#define HAD_FIFO_SIZE		0 /* fifo not being used */