2011-05-20 14:26:45

by Michael Williamson

Subject: [PATCH v1 RESEND] audio: tlv320aic26: fix PLL register configuration

The current PLL configuration code for the tlc320aic26 codec appears to assume a
hardcoded system clock of 12 MHz. Use the clock value provided by the DAI_OPS
API for the calculation.

Tested using a MityDSP-L138 platform providing a 24.576 MHz clock.

Signed-off-by: Michael Williamson <[email protected]>
Acked-by: Mark Brown <[email protected]>
---
This got bounced by the alsa-devel list (I wasn't on list). I'm not sure
whose tree this needs to go through, but given the lack of response
I'm guessing alsa-devel. If I'm missing a list, any advice would be
appreciated.

Changes from V0:
- Added some parens for clarification
- Added some comments to describe what the computations were attempting to do

sound/soc/codecs/tlv320aic26.c | 14 +++++++++++---
1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/sound/soc/codecs/tlv320aic26.c b/sound/soc/codecs/tlv320aic26.c
index e2a7608..7859bdc 100644
--- a/sound/soc/codecs/tlv320aic26.c
+++ b/sound/soc/codecs/tlv320aic26.c
@@ -161,10 +161,18 @@ static int aic26_hw_params(struct snd_pcm_substream *substream,
dev_dbg(&aic26->spi->dev, "bad format\n"); return -EINVAL;
}

- /* Configure PLL */
+ /**
+ * Configure PLL
+ * fsref = (mclk * PLLM) / 2048
+ * where PLLM = J.DDDD (DDDD register ranges from 0 to 9999, decimal)
+ */
pval = 1;
- jval = (fsref == 44100) ? 7 : 8;
- dval = (fsref == 44100) ? 5264 : 1920;
+ /* compute J portion of multiplier */
+ jval = fsref / (aic26->mclk / 2048);
+ /* compute fractional DDDD component of multiplier */
+ dval = fsref - (jval * (aic26->mclk / 2048));
+ dval = (10000 * dval) / (aic26->mclk / 2048);
+ dev_dbg(&aic26->spi->dev, "Setting PLLM to %d.%04d\n", jval, dval);
qval = 0;
reg = 0x8000 | qval << 11 | pval << 8 | jval << 2;
aic26_reg_write(codec, AIC26_REG_PLL_PROG1, reg);
--
1.7.0.4

2011-05-21 11:08:29

by Liam Girdwood

Subject: Re: [PATCH v1 RESEND] audio: tlv320aic26: fix PLL register configuration

On Fri, 2011-05-20 at 10:26 -0400, Michael Williamson wrote:
> The current PLL configuration code for the tlc320aic26 codec appears to assume a
> hardcoded system clock of 12 MHz. Use the clock value provided by the DAI_OPS
> API for the calculation.
>
> Tested using a MityDSP-L138 platform providing a 24.576 MHz clock.
>
> Signed-off-by: Michael Williamson <[email protected]>
> Acked-by: Mark Brown <[email protected]>
> ---
> This got bounced by the alsa-devel list (I wasn't on list). I'm not sure
> whose tree this needs to go through, but given the lack of response
> I'm guessing alsa-devel. If I'm missing a list, any advice would be
> appreciated.

Applied.

Thanks

Liam