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@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;
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); + else + omap_enable_dma_irq(prtd->dma_ch, OMAP_DMA_FRAME_IRQ);
return 0; }