From: Raffaele Recalcati raffaele.recalcati@bticino.it
i2s_fast_clock switch can be used to have a better approximate frequency. The waveform will be not symmetric.
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 --- arch/arm/mach-davinci/include/mach/asp.h | 7 +++++++ sound/soc/davinci/davinci-i2s.c | 24 +++++++++++++++++++----- 2 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/arch/arm/mach-davinci/include/mach/asp.h b/arch/arm/mach-davinci/include/mach/asp.h index 314570d..2d8f8af 100644 --- a/arch/arm/mach-davinci/include/mach/asp.h +++ b/arch/arm/mach-davinci/include/mach/asp.h @@ -63,6 +63,13 @@ struct snd_platform_data { unsigned sram_size_playback; unsigned sram_size_capture;
+ /* + * This define works when both clock and FS are output for the cpu + * and makes clock very fast (FS is not symmetrical, but sampling + * frequency is better approximated + */ + bool i2s_fast_clock; + /* To be used when cpu gets clock from external pin */ int clk_input_pin;
diff --git a/sound/soc/davinci/davinci-i2s.c b/sound/soc/davinci/davinci-i2s.c index e478be9..0af5bae 100644 --- a/sound/soc/davinci/davinci-i2s.c +++ b/sound/soc/davinci/davinci-i2s.c @@ -150,6 +150,7 @@ struct davinci_mcbsp_dev { */ unsigned enable_channel_combine:1;
+ bool i2s_fast_clock; unsigned int fmt; int clk_div; int clk_input_pin; @@ -443,11 +444,23 @@ 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_fast_clock) { + 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; @@ -643,6 +656,7 @@ static int davinci_i2s_probe(struct platform_device *pdev) pdata->sram_size_playback; dev->dma_params[SNDRV_PCM_STREAM_CAPTURE].sram_size = pdata->sram_size_capture; + dev->i2s_fast_clock = pdata->i2s_fast_clock; dev->clk_input_pin = pdata->clk_input_pin; } dev->clk = clk_get(&pdev->dev, NULL);