Enhance period index accuracy, particularly just before buffer rewind, by making use of DMA interrupt status flags in addition to simply counting interrupts
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@tis.icnet.pl
--- --- linux-2.6.31-rc5/sound/soc/omap/omap-pcm.c.orig 2009-08-10 08:31:08.000000000 +0200 +++ linux-2.6.31-rc5/sound/soc/omap/omap-pcm.c 2009-08-10 08:55:09.000000000 +0200 @@ -68,13 +68,28 @@ 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 (prtd->period_index >= 0) { - if (++prtd->period_index == runtime->periods) { + if (stat & OMAP_DMA_LAST_IRQ) { + /* last period of a buffer has been started */ + if (prtd->period_index == (runtime->periods - 1)) { + /* we are in sync, do nothing */ + spin_unlock_irqrestore(&prtd->lock, flags); + return; + } else if (prtd->period_index >= 0) { + /* possible IRQ loss, update the pointer */ + prtd->period_index = runtime->periods - 1; + } + } else if (prtd->period_index >= 0) { + /* playback in progress - increment the counter, + * check for end of buffer */ + if ((++prtd->period_index >= runtime->periods) || + (stat & OMAP_DMA_BLOCK_IRQ)) { + /* end of buffer reached, loop back */ prtd->period_index = 0; } } spin_unlock_irqrestore(&prtd->lock, flags); - } + } else if (stat & OMAP_DMA_LAST_IRQ) + return;
snd_pcm_period_elapsed(substream); } @@ -175,7 +190,8 @@ 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); + omap_enable_dma_irq(prtd->dma_ch, OMAP_DMA_FRAME_IRQ | + (cpu_is_omap1510() ? OMAP_DMA_LAST_IRQ : 0));
return 0; }