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Commit 0d6c9774 authored by Troy Kisky's avatar Troy Kisky Committed by Mark Brown
Browse files

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



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

Signed-off-by: default avatarTroy Kisky <troy.kisky@boundarydevices.com>
Acked-by: default avatarLiam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
parent 41b51dd4

arch/arm/mach-davinci/include/mach/asp.h

+6 −0
Original line number Diff line number Diff line
@@ -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;

sound/soc/davinci/davinci-i2s.c

+55 −19
Original line number Diff line number Diff line
@@ -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;