linux-kernel - Re: [PATCH 11/11] ASoC: omap-pcm: Convert to use dmaengine

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Date:	Wed, 12 Sep 2012 17:35:56 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>, Tony Lindgren <tony@...mide.com>,
	Vinod Koul <vinod.koul@...el.com>, Dan Williams <djbw@...com>,
	Jarkko Nikula <jarkko.nikula@...mer.com>,
	alsa-devel@...a-project.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Janusz Krzysztofik <jkrzyszt@....icnet.pl>,
	Ricardo Neri <ricardo.neri@...com>
Subject: Re: [PATCH 11/11] ASoC: omap-pcm: Convert to use dmaengine

On 09/12/2012 03:53 PM, Peter Ujfalusi wrote:
> I need to look at this, but at first look we do wait for the drain in
> omap_stop_dma(). We used to use omap_stop_dma/omap_start_dma for pause/resume
> operations.
> But sDMA also have a bit: CDPi: PAUSE_LINK_LIST which should do what we are
> looking for.
> Need to read the relevant parts of the TRM, but AFAIK we are using normal mode
> with linked list (self linking).
> I already have the patch for this, I just need to test it on HW.

We can get the PAUSE/RESUME work either:
1.
drivers/dma/omap-dma.c
static int omap_dma_pause(struct omap_chan *c)
 {
-       /* FIXME: not supported by platform private API */
-       return -EINVAL;
+       /* Only in cyclic mode */
+       if (!c->cyclic)
+               return -EINVAL;
+
+       if (!c->paused) {
+               omap_stop_dma(c->dma_ch);
+               c->paused = true;
+       }
+
+       return 0;
 }

 static int omap_dma_resume(struct omap_chan *c)
 {
-       /* FIXME: not supported by platform private API */
-       return -EINVAL;
+       /* Only in cyclic mode */
+       if (!c->cyclic)
+               return -EINVAL;
+
+       if (c->paused) {
+               omap_start_dma(c->dma_ch);
+               c->paused = false;
+       }
+
+       return 0;
 }


2.
arch/arm/plat-omap/dma.c
+void omap_pause_linked_dma(int lch)
+{
+       u32 l;
+       unsigned long flags;
+
+       local_irq_save(flags);
+       l = p->dma_read(CDP, lch);
+       l |= 0x80; /* PAUSE_LINK_LIST */
+       p->dma_write(l, CDP, lch);
+       local_irq_restore(flags);
+}
+EXPORT_SYMBOL(omap_pause_linked_dma);
+
+void omap_resume_linked_dma(int lch)
+{
+       u32 l;
+       unsigned long flags;
+
+       local_irq_save(flags);
+       l = p->dma_read(CDP, lch);
+       l &= (~0x80); /* PAUSE_LINK_LIST */
+       p->dma_write(l, CDP, lch);
+       local_irq_restore(flags);
+}
+EXPORT_SYMBOL(omap_resume_linked_dma);

drivers/dma/omap-dma.c
 static int omap_dma_pause(struct omap_chan *c)
 {
-       /* FIXME: not supported by platform private API */
-       return -EINVAL;
+       /* Only in cyclic mode */
+       if (!c->cyclic)
+               return -EINVAL;
+
+       if (!c->paused) {
+               omap_pause_linked_dma(c->dma_ch);
+               c->paused = true;
+       }
+
+       return 0;
 }

 static int omap_dma_resume(struct omap_chan *c)
 {
-       /* FIXME: not supported by platform private API */
-       return -EINVAL;
+       /* Only in cyclic mode */
+       if (!c->cyclic)
+               return -EINVAL;
+
+       if (c->paused) {
+               omap_resume_linked_dma(c->dma_ch);
+               c->paused = false;
+       }
+
+       return 0;
 }


Both works fine (have tested it on BeagleBoard with mplayer).
With [1] we have identical way of dealing with the PAUSE/RESUME as we had
previously, so it is know to work fine on OMAP1/2/3/4/5

We have never used [2] in the past, but I think that is not going to work on
OMAP1 and OMAP2420. Also we need to add code to arch/arm/plat-omap/dma.c for
this...

I can resend the series with either of these to fix this regression caused by
the dmaengine conversion (after cleanup off course).

-- 
Péter
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