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

[Sascha Hauer]

(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


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