Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760486Ab3DCLSM (ORCPT ); Wed, 3 Apr 2013 07:18:12 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:57683 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760313Ab3DCLSK (ORCPT ); Wed, 3 Apr 2013 07:18:10 -0400 From: Peter Ujfalusi To: Russell King - ARM Linux , Vinod Koul , Dan Williams CC: Tony Lindgren , Jarkko Nikula , Santosh Shilimkar , Felipe Balbi , , , , Peter Meerwald Subject: [RFC v2] dmaengine: omap-dma: Start DMA without delay for cyclic channels Date: Wed, 3 Apr 2013 13:17:42 +0200 Message-ID: <1364987862-14597-1-git-send-email-peter.ujfalusi@ti.com> X-Mailer: git-send-email 1.8.1.5 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1969 Lines: 61 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) { - 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); } -- 1.8.1.5 -- 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/