ASoC: imx dma tx burst size set to 6 and to 4 ?

[Sascha Hauer]

On Mon, Jul 04, 2011 at 10:00:34AM +0200, javier Martin wrote:
> 2011/7/4 Sascha Hauer <s.hauer at pengutronix.de>:
> > (Added Javier to Cc)
> >
> > On Thu, Jun 30, 2011 at 08:25:29AM +0200, Lambrecht Jürgen wrote:
> >> Hello,
> >>
> >> There is an inconsistency in this code:
> >>
> >> /sound/soc/imx/imx-ssi.c:         ssi->dma_params_tx.burstsize = 4;
> >> /sound/soc/imx/imx-pcm-dma-mx2.c: ssi->dma_params_tx.burstsize = 6;
> >>
> >> Datasheet:
> >> This sets the field TFWM0 in register SFCSR (SSI_SFCSR_TFWM0): the
> >> number of data words needed to set the empty flag (TFE0). Can be set
> >> from 1 to 8; FIFO size is 8 words (of 24b). And this is also the DMA
> >> burst size.
> >>
> >> Which is best depends on the application (the higher the more efficient,
> >> but the more risk for a FIFO underrun). I would take 4.
> >>
> >> But I guess it should only be set at 1 place, and what is then the best
> >> place?
> >
> > We need different burstsize settings for the FIQ driver and for the DMA
> > driver. For this reason the original intention was to set these values
> > in sound/soc/imx/imx-pcm-dma-mx2.c and in sound/soc/imx/imx-pcm-fiq.c.
> >
> >
> >> commit 0a93421b6adf8ba127b3eafc4c16e3a14017e2ae
> >> Author: Javier Martin <javier.martin at vista-silicon.com>
> >> Date:   Tue Mar 1 15:02:06 2011 +0100
> >>
> >>     ASoC: Fix burstsize and DSP_B format problems in imx-ssi.
> >>
> >>     When choosing IMX_DMA flag, burtsizes are set to its default
> >>     value (0) which leads to driver malfunction. Change them to 4.
> >>
> >>     DSP_B interface needs additional flag to match DSP_B formats
> >>     as described in several codecs as wm8741 and aic3205.
> >>
> >>     Signed-off-by: Javier Martin <javier.martin at vista-silicon.com>
> >>     Acked-by: Liam Girdwood <lrg at slimlogic.co.uk>
> >>     Signed-off-by: Mark Brown <broonie at opensource.wolfsonmicro.com>
> >>
> >> diff --git a/sound/soc/imx/imx-ssi.c b/sound/soc/imx/imx-ssi.c
> >> index 30894ea..bc92ec6 100644
> >> --- a/sound/soc/imx/imx-ssi.c
> >> +++ b/sound/soc/imx/imx-ssi.c
> >> @@ -108,7 +108,7 @@ static int imx_ssi_set_dai_fmt(struct snd_soc_dai *cpu_dai, unsigned int fmt)
> >>               break;
> >>       case SND_SOC_DAIFMT_DSP_B:
> >>               /* data on rising edge of bclk, frame high with data */
> >> -             strcr |= SSI_STCR_TFSL;
> >> +             strcr |= SSI_STCR_TFSL | SSI_STCR_TXBIT0;
> >>               break;
> >>       case SND_SOC_DAIFMT_DSP_A:
> >>               /* data on rising edge of bclk, frame high 1clk before data */
> >> @@ -656,6 +656,9 @@ static int imx_ssi_probe(struct platform_device *pdev)
> >>       ssi->dma_params_rx.dma_addr = res->start + SSI_SRX0;
> >>       ssi->dma_params_tx.dma_addr = res->start + SSI_STX0;
> >>
> >> +     ssi->dma_params_tx.burstsize = 4;
> >> +     ssi->dma_params_rx.burstsize = 4;
> >> +
> >
> > Javier, is this hunk necessary? From what I see these values should be
> > overwritten later anyway.
> >
> > Sascha
> 
> Hi,
> without this hunk, both burstsizes where set to 0. This was checked
> experimentally:
> 
> - Audio didn't work properly.
> - Some runtime printk's showed that burstsizes where set to 0.
> 
> It seems assignments in imx-pcm-dma-mx2.c file are done at a place
> they do not take effect.

I just did a quick test. In imx_ssi_dai_probe where the values are
actually used they are correctly initialized.
Anyway, the current way to initialize these values seems a bit strange.
Maybe we should pass the burstsize parameters in imx_pcm_new instead.

Sascha

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