Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760987Ab3DCLXM (ORCPT ); Wed, 3 Apr 2013 07:23:12 -0400 Received: from bear.ext.ti.com ([192.94.94.41]:50994 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760840Ab3DCLXJ (ORCPT ); Wed, 3 Apr 2013 07:23:09 -0400 Message-ID: <515C117A.6060700@ti.com> Date: Wed, 3 Apr 2013 16:54:42 +0530 From: Santosh Shilimkar User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Peter Ujfalusi CC: Russell King - ARM Linux , Vinod Koul , Dan Williams , Tony Lindgren , Jarkko Nikula , Felipe Balbi , , , , Peter Meerwald Subject: Re: [RFC v2] dmaengine: omap-dma: Start DMA without delay for cyclic channels References: <1364987862-14597-1-git-send-email-peter.ujfalusi@ti.com> In-Reply-To: <1364987862-14597-1-git-send-email-peter.ujfalusi@ti.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2236 Lines: 64 On Wednesday 03 April 2013 04:47 PM, Peter Ujfalusi wrote: > 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 > Signed-off-by: Peter Ujfalusi > --- > Hi Russell, > > Instead of removing the tasklet we can identify the DMA channel used by audio > based on the cyclic flag of the channel. > I think this can be used as a short term solution to fix the audio channel shift > issue and later when we have the dynamic DMA channel allocation we can adjust > the code. > > Regards, > Peter > > drivers/dma/omap-dma.c | 20 ++++++++++++++------ > 1 file changed, 14 insertions(+), 6 deletions(-) > > diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c > index 2ea3d7e..ec3fc4f 100644 > --- a/drivers/dma/omap-dma.c > +++ b/drivers/dma/omap-dma.c > @@ -282,12 +282,20 @@ static void omap_dma_issue_pending(struct dma_chan *chan) > > spin_lock_irqsave(&c->vc.lock, flags); > if (vchan_issue_pending(&c->vc) && !c->desc) { If you add "!c->cyclic" in above if then you can avoid indentation change and just have else for cyclic case. > - 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); > } > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/