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@xxxxxxxxxxxx>
---
--- 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;
}
--
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