Allow the left and right 16 bit samples to be shifted out as 1
32 bit sample.
Signed-off-by: Troy Kisky <troy.kisky@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/mach-davinci/include/mach/asp.h | 6 +++
sound/soc/davinci/davinci-i2s.c | 73 ++++++++++++++++++++++-------
2 files changed, 61 insertions(+), 18 deletions(-)
diff --git a/arch/arm/mach-davinci/include/mach/asp.h b/arch/arm/mach-davinci/include/mach/asp.h
index cdf1f44..73b60b6 100644
--- a/arch/arm/mach-davinci/include/mach/asp.h
+++ b/arch/arm/mach-davinci/include/mach/asp.h
@@ -37,6 +37,12 @@ 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 disable_channel_combine:1;
/* McASP specific fields */
int tdm_slots;
diff --git a/sound/soc/davinci/davinci-i2s.c b/sound/soc/davinci/davinci-i2s.c
index 2a56fb7..9587e00 100644
--- a/sound/soc/davinci/davinci-i2s.c
+++ b/sound/soc/davinci/davinci-i2s.c
@@ -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,
+};
+
static struct davinci_pcm_dma_params davinci_i2s_pcm_out = {
.name = "I2S PCM Stereo out",
};
@@ -113,6 +130,27 @@ struct davinci_mcbsp_dev {
u32 pcr;
struct clk *clk;
struct davinci_pcm_dma_params *dma_params[2];
+ /*
+ * 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 disable_channel_combine:1;
};
static inline void davinci_mcbsp_write_reg(struct davinci_mcbsp_dev *dev,
@@ -359,6 +397,8 @@ 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);
@@ -388,26 +428,22 @@ 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;
}
-
- rcr |= DAVINCI_MCBSP_RCR_RFRLEN1(1);
- xcr |= DAVINCI_MCBSP_XCR_XFRLEN1(1);
+ if (params_channels(params) == 2) {
+ element_cnt = 2;
+ if (double_fmt[fmt] && !dev->disable_channel_combine) {
+ element_cnt = 1;
+ fmt = double_fmt[fmt];
+ }
+ }
+ dma_params->data_type = data_type[fmt];
+ 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);
@@ -523,7 +559,8 @@ static int davinci_i2s_probe(struct platform_device *pdev)
ret = -ENOMEM;
goto err_release_region;
}
-
+ if (pdata)
+ dev->disable_channel_combine = pdata->disable_channel_combine;
dev->clk = clk_get(&pdev->dev, NULL);
if (IS_ERR(dev->clk)) {
ret = -ENODEV;
--
1.5.6.3
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