[alsa-devel] [RFC][PATCH 3/3 v2] ASoC: OMAP: Enhance OMAP1510 DMA progress software counter

[Jarkko Nikula]

On Tue, 11 Aug 2009 01:07:10 +0200
Janusz Krzysztofik <jkrzyszt at tis.icnet.pl> wrote:

> Enhance period index accuracy, particularly just before buffer rewind, by
> making use of DMA interrupt status flags in addition to simply counting up
> interrupts.
> 
> Corrections since v1:
> 1. Fix buggy DMA interrupt handling in case of multiple status flags set in
>    parallel.
> 2. Enable OMAP_DMA_LAST_IRQ only for playback on OMAP1510.
> 
> This patch applies on top of patch 2 from this series:
> [RFC][PATCH 2/3] ASoC: OMAP: Make use of DMA channel self linking on OMAP1510
> 
> Created against linux-2.6.31-rc5.
> 
> Tested on Amstrad Delta.
> 
> Signed-off-by: Janusz Krzysztofik <jkrzyszt at tis.icnet.pl>
> 
> ---
> --- linux-2.6.31-rc5/sound/soc/omap/omap-pcm.c.orig	2009-08-10 22:41:25.000000000 +0200
> +++ linux-2.6.31-rc5/sound/soc/omap/omap-pcm.c	2009-08-10 23:15:46.000000000 +0200
> @@ -68,13 +68,27 @@ static void omap_pcm_dma_irq(int ch, u16
>  		 * that can be used by omap_pcm_pointer() instead.
>  		 */
>  		spin_lock_irqsave(&prtd->lock, flags);
> +		if ((stat == OMAP_DMA_LAST_IRQ) &&
> +				(prtd->period_index == runtime->periods - 1)) {
> +			/* we are in sync, do nothing */
> +			spin_unlock_irqrestore(&prtd->lock, flags);
> +			return;
> +		}
>  		if (prtd->period_index >= 0) {
> -			if (++prtd->period_index == runtime->periods) {
> +			if (stat & OMAP_DMA_BLOCK_IRQ) {
> +				/* end of buffer reached, loop back */
> +				prtd->period_index = 0;
> +			} else if (stat & OMAP_DMA_LAST_IRQ) {
> +				/* update the counter for the last period */
> +				prtd->period_index = runtime->periods - 1;
> +			} else if (++prtd->period_index >= runtime->periods) {
> +				/* end of buffer missed? loop back */
>  				prtd->period_index = 0;
>  			}
>  		}
>  		spin_unlock_irqrestore(&prtd->lock, flags);
> -	}
> +	} else if (stat == OMAP_DMA_LAST_IRQ)
> +		return;
>  
Is this test needed? This interrupt is set only for playback on
omap1510 so this looks null-op.

>  	snd_pcm_period_elapsed(substream);
>  }
> @@ -175,7 +189,12 @@ static int omap_pcm_prepare(struct snd_p
>  	dma_params.frame_count	= runtime->periods;
>  	omap_set_dma_params(prtd->dma_ch, &dma_params);
>  
> -	omap_enable_dma_irq(prtd->dma_ch, OMAP_DMA_FRAME_IRQ);
> +	if ((cpu_is_omap1510()) &&
> +			(substream->stream == SNDRV_PCM_STREAM_PLAYBACK))
> +		omap_enable_dma_irq(prtd->dma_ch, OMAP_DMA_FRAME_IRQ |
> +							OMAP_DMA_LAST_IRQ);

Indent OMAP_DMA_LAST_IRQ with tab(s) and spaces to the same column
than OMAP_DMA_FRAME_IRQ. Looks nicer then. Should the
OMAP_DMA_BLOCK_IRQ to be set since it is handled in omap_pcm_dma_irq?


-- 
Jarkko