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ASoC: DaVinci: i2s, reduce underruns by combining into 1 element

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Allow the left and right 16 bit samples to be shifted out as 1
32 bit sample.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
This commit is contained in:
Troy Kisky 2009-11-18 17:49:51 -07:00 committed by Mark Brown
parent 41b51dd47e
commit 0d6c977429
2 changed files with 61 additions and 19 deletions
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6
arch/arm/mach-davinci/include/mach/asp.h
View file

@ -51,6 +51,12 @@ struct snd_platform_data {
u32 rx_dma_offset;
enum dma_event_q eventq_no; /* event queue number */
unsigned int codec_fmt;
/*
* Allowing this is more efficient and eliminates left and right swaps
* caused by underruns, but will swap the left and right channels
* when compared to previous behavior.
*/
unsigned enable_channel_combine:1;
/* McASP specific fields */
int tdm_slots;

74
sound/soc/davinci/davinci-i2s.c
View file

@ -97,6 +97,23 @@ enum {
DAVINCI_MCBSP_WORD_32,
};
static const unsigned char data_type[SNDRV_PCM_FORMAT_S32_LE + 1] = {
[SNDRV_PCM_FORMAT_S8] = 1,
[SNDRV_PCM_FORMAT_S16_LE] = 2,
[SNDRV_PCM_FORMAT_S32_LE] = 4,
};
static const unsigned char asp_word_length[SNDRV_PCM_FORMAT_S32_LE + 1] = {
[SNDRV_PCM_FORMAT_S8] = DAVINCI_MCBSP_WORD_8,
[SNDRV_PCM_FORMAT_S16_LE] = DAVINCI_MCBSP_WORD_16,
[SNDRV_PCM_FORMAT_S32_LE] = DAVINCI_MCBSP_WORD_32,
};
static const unsigned char double_fmt[SNDRV_PCM_FORMAT_S32_LE + 1] = {
[SNDRV_PCM_FORMAT_S8] = SNDRV_PCM_FORMAT_S16_LE,
[SNDRV_PCM_FORMAT_S16_LE] = SNDRV_PCM_FORMAT_S32_LE,
};
struct davinci_mcbsp_dev {
struct davinci_pcm_dma_params dma_params[2];
void __iomem *base;
@ -105,6 +122,27 @@ struct davinci_mcbsp_dev {
int mode;
u32 pcr;
struct clk *clk;
/*
* Combining both channels into 1 element will at least double the
* amount of time between servicing the dma channel, increase
* effiency, and reduce the chance of overrun/underrun. But,
* it will result in the left & right channels being swapped.
*
* If relabeling the left and right channels is not possible,
* you may want to let the codec know to swap them back.
*
* It may allow x10 the amount of time to service dma requests,
* if the codec is master and is using an unnecessarily fast bit clock
* (ie. tlvaic23b), independent of the sample rate. So, having an
* entire frame at once means it can be serviced at the sample rate
* instead of the bit clock rate.
*
* In the now unlikely case that an underrun still
* occurs, both the left and right samples will be repeated
* so that no pops are heard, and the left and right channels
* won't end up being swapped because of the underrun.
*/
unsigned enable_channel_combine:1;
};
static inline void davinci_mcbsp_write_reg(struct davinci_mcbsp_dev *dev,
@ -344,6 +382,8 @@ static int davinci_i2s_hw_params(struct snd_pcm_substream *substream,
int mcbsp_word_length;
unsigned int rcr, xcr, srgr;
u32 spcr;
snd_pcm_format_t fmt;
unsigned element_cnt = 1;
/* general line settings */
spcr = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_SPCR_REG);
@ -373,29 +413,24 @@ static int davinci_i2s_hw_params(struct snd_pcm_substream *substream,
xcr |= DAVINCI_MCBSP_XCR_XDATDLY(1);
}
/* Determine xfer data type */
switch (params_format(params)) {
case SNDRV_PCM_FORMAT_S8:
dma_params->data_type = 1;
mcbsp_word_length = DAVINCI_MCBSP_WORD_8;
break;
case SNDRV_PCM_FORMAT_S16_LE:
dma_params->data_type = 2;
mcbsp_word_length = DAVINCI_MCBSP_WORD_16;
break;
case SNDRV_PCM_FORMAT_S32_LE:
dma_params->data_type = 4;
mcbsp_word_length = DAVINCI_MCBSP_WORD_32;
break;
default:
fmt = params_format(params);
if ((fmt > SNDRV_PCM_FORMAT_S32_LE) || !data_type[fmt]) {
printk(KERN_WARNING "davinci-i2s: unsupported PCM format\n");
return -EINVAL;
}
dma_params->acnt = dma_params->data_type;
if (params_channels(params) == 2) {
element_cnt = 2;
if (double_fmt[fmt] && dev->enable_channel_combine) {
element_cnt = 1;
fmt = double_fmt[fmt];
}
}
dma_params->acnt = dma_params->data_type = data_type[fmt];
dma_params->fifo_level = 0;
rcr |= DAVINCI_MCBSP_RCR_RFRLEN1(1);
xcr |= DAVINCI_MCBSP_XCR_XFRLEN1(1);
mcbsp_word_length = asp_word_length[fmt];
rcr |= DAVINCI_MCBSP_RCR_RFRLEN1(element_cnt - 1);
xcr |= DAVINCI_MCBSP_XCR_XFRLEN1(element_cnt - 1);
rcr |= DAVINCI_MCBSP_RCR_RWDLEN1(mcbsp_word_length) |
DAVINCI_MCBSP_RCR_RWDLEN2(mcbsp_word_length);
@ -510,7 +545,8 @@ static int davinci_i2s_probe(struct platform_device *pdev)
ret = -ENOMEM;
goto err_release_region;
}
if (pdata)
dev->enable_channel_combine = pdata->enable_channel_combine;
dev->clk = clk_get(&pdev->dev, NULL);
if (IS_ERR(dev->clk)) {
ret = -ENODEV;