This is a note to let you know that I've just added the patch titled
dmaengine: omap-dma: Start DMA without delay for cyclic channels
to the 3.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dmaengine-omap-dma-start-dma-without-delay-for-cyclic-channels.patch
and it can be found in the queue-3.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 765024697807ad1e1cac332aa891253ca4a339da Mon Sep 17 00:00:00 2001
From: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
Date: Tue, 9 Apr 2013 16:33:06 +0200
Subject: dmaengine: omap-dma: Start DMA without delay for cyclic channels
From: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
commit 765024697807ad1e1cac332aa891253ca4a339da upstream.
cyclic DMA is only used by audio which needs DMA to be started without a
delay.
If the DMA for audio is started using the tasklet we experience random
channel switch (to be more precise: channel shift).
Reported-by: Peter Meerwald <pmeerw@xxxxxxxxxx>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
Acked-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Vinod Koul <vinod.koul@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/dma/omap-dma.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
--- a/drivers/dma/omap-dma.c
+++ b/drivers/dma/omap-dma.c
@@ -276,12 +276,20 @@ static void omap_dma_issue_pending(struc
spin_lock_irqsave(&c->vc.lock, flags);
if (vchan_issue_pending(&c->vc) && !c->desc) {
- struct omap_dmadev *d = to_omap_dma_dev(chan->device);
- spin_lock(&d->lock);
- if (list_empty(&c->node))
- list_add_tail(&c->node, &d->pending);
- spin_unlock(&d->lock);
- tasklet_schedule(&d->task);
+ /*
+ * c->cyclic is used only by audio and in this case the DMA need
+ * to be started without delay.
+ */
+ if (!c->cyclic) {
+ struct omap_dmadev *d = to_omap_dma_dev(chan->device);
+ spin_lock(&d->lock);
+ if (list_empty(&c->node))
+ list_add_tail(&c->node, &d->pending);
+ spin_unlock(&d->lock);
+ tasklet_schedule(&d->task);
+ } else {
+ omap_dma_start_desc(c);
+ }
}
spin_unlock_irqrestore(&c->vc.lock, flags);
}
Patches currently in stable-queue which might be from peter.ujfalusi@xxxxxx are
queue-3.8/dmaengine-omap-dma-start-dma-without-delay-for-cyclic-channels.patch
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