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authorRaffaele Recalcati <raffaele.recalcati@bticino.it>2010-07-06 10:39:04 +0200
committerMark Brown <broonie@opensource.wolfsonmicro.com>2010-07-06 23:54:07 +0900
commitd9823ed9fa3126097dfd2bbce6dc33957c1be728 (patch)
treea929aead29f43232b408b182ce5a5e5e4c8654a0 /sound/soc/davinci/davinci-i2s.c
parentec6375533748806a1a49dad7ce124cc02886854a (diff)
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ASoC: DaVinci: More accurate continuous serial clock for McBSP (I2S)
i2s_accurate_sck switch can be used to have a better approximate sampling frequency. The clock is an externally visible bit clock and it is named i2s continuous serial clock (I2S_SCK). The trade off is between more accurate clock (fast clock) and less accurate clock (slow clock). The waveform will be not symmetric. Probably it is possible to get a better algorithm for calculating the divider, trying to keep a slower clock as possible. This patch has been developed against the http://git.kernel.org/pub/scm/linux/kernel/git/khilman/linux-davinci.git git tree and has been tested on bmx board (similar to dm365 evm, but using uda1345 as external audio codec). Signed-off-by: Raffaele Recalcati <raffaele.recalcati@bticino.it> Signed-off-by: Davide Bonfanti <davide.bonfanti@bticino.it> Acked-by: Liam Girdwood <lrg@slimlogic.co.uk> Acked-by: Sudhakar Rajashekhara <sudhakar.raj@ti.com> Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Diffstat (limited to 'sound/soc/davinci/davinci-i2s.c')
-rw-r--r--sound/soc/davinci/davinci-i2s.c24
1 files changed, 19 insertions, 5 deletions
diff --git a/sound/soc/davinci/davinci-i2s.c b/sound/soc/davinci/davinci-i2s.c
index ba5644b..b251bc9 100644
--- a/sound/soc/davinci/davinci-i2s.c
+++ b/sound/soc/davinci/davinci-i2s.c
@@ -155,6 +155,7 @@ struct davinci_mcbsp_dev {
unsigned int fmt;
int clk_div;
int clk_input_pin;
+ bool i2s_accurate_sck;
};
static inline void davinci_mcbsp_write_reg(struct davinci_mcbsp_dev *dev,
@@ -447,11 +448,23 @@ static int davinci_i2s_hw_params(struct snd_pcm_substream *substream,
DAVINCI_MCBSP_SRGR_CLKSM;
srgr |= DAVINCI_MCBSP_SRGR_FWID(mcbsp_word_length *
8 - 1);
- /* symmetric waveforms */
- clk_div = freq / (mcbsp_word_length * 16) /
- params->rate_num * params->rate_den;
- srgr |= DAVINCI_MCBSP_SRGR_FPER(mcbsp_word_length *
- 16 - 1);
+ if (dev->i2s_accurate_sck) {
+ clk_div = 256;
+ do {
+ framesize = (freq / (--clk_div)) /
+ params->rate_num *
+ params->rate_den;
+ } while (((framesize < 33) || (framesize > 4095)) &&
+ (clk_div));
+ clk_div--;
+ srgr |= DAVINCI_MCBSP_SRGR_FPER(framesize - 1);
+ } else {
+ /* symmetric waveforms */
+ clk_div = freq / (mcbsp_word_length * 16) /
+ params->rate_num * params->rate_den;
+ srgr |= DAVINCI_MCBSP_SRGR_FPER(mcbsp_word_length *
+ 16 - 1);
+ }
clk_div &= 0xFF;
srgr |= clk_div;
break;
@@ -662,6 +675,7 @@ static int davinci_i2s_probe(struct platform_device *pdev)
dev->dma_params[SNDRV_PCM_STREAM_CAPTURE].sram_size =
pdata->sram_size_capture;
dev->clk_input_pin = pdata->clk_input_pin;
+ dev->i2s_accurate_sck = pdata->i2s_accurate_sck;
}
dev->clk = clk_get(&pdev->dev, NULL);
if (IS_ERR(dev->clk)) {