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

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Message-Id: <200908110107.11485.jkrzyszt@tis.icnet.pl>
Date:	Tue, 11 Aug 2009 01:07:10 +0200
From:	Janusz Krzysztofik <jkrzyszt@....icnet.pl>
To:	Jarkko Nikula <jhnikula@...il.com>
Cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Peter Ujfalusi <peter.ujfalusi@...ia.com>,
	Tony Lindgren <tony@...mide.com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.arm.linux.org.uk" 
	<linux-arm-kernel@...ts.arm.linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [RFC][PATCH 3/3 v2] ASoC: OMAP: Enhance OMAP1510 DMA progress software counter

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@....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;
 }
--
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