dmaengine Archive on lore.kernel.org
 help / color / Atom feed
* [PATCH AUTOSEL 4.4 24/44] dmaengine: dma-jz4780: Further residue status fix
       [not found] <20191108114721.15944-1-sashal@kernel.org>
@ 2019-11-08 11:47 ` Sasha Levin
  0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2019-11-08 11:47 UTC (permalink / raw)
  To: linux-kernel, stable
  Cc: Daniel Silsby, Paul Cercueil, Mathieu Malaterre, Vinod Koul,
	Sasha Levin, dmaengine

From: Daniel Silsby <dansilsby@gmail.com>

[ Upstream commit 83ef4fb7556b6a673f755da670cbacab7e2c7f1b ]

Func jz4780_dma_desc_residue() expects the index to the next hw
descriptor as its last parameter. Caller func jz4780_dma_tx_status(),
however, applied modulus before passing it. When the current hw
descriptor was last in the list, the index passed became zero.

The resulting excess of reported residue especially caused problems
with cyclic DMA transfer clients, i.e. ALSA AIC audio output, which
rely on this for determining current DMA location within buffer.

Combined with the recent and related residue-reporting fixes, spurious
ALSA audio underruns on jz4770 hardware are now fixed.

Signed-off-by: Daniel Silsby <dansilsby@gmail.com>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/dma/dma-jz4780.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
index 8344b7c91fe35..1d01e3805f9c2 100644
--- a/drivers/dma/dma-jz4780.c
+++ b/drivers/dma/dma-jz4780.c
@@ -576,7 +576,7 @@ static enum dma_status jz4780_dma_tx_status(struct dma_chan *chan,
 					to_jz4780_dma_desc(vdesc), 0);
 	} else if (cookie == jzchan->desc->vdesc.tx.cookie) {
 		txstate->residue = jz4780_dma_desc_residue(jzchan, jzchan->desc,
-			  (jzchan->curr_hwdesc + 1) % jzchan->desc->count);
+					jzchan->curr_hwdesc + 1);
 	} else
 		txstate->residue = 0;
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] only message in thread

only message in thread, back to index

Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <20191108114721.15944-1-sashal@kernel.org>
2019-11-08 11:47 ` [PATCH AUTOSEL 4.4 24/44] dmaengine: dma-jz4780: Further residue status fix Sasha Levin

dmaengine Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/dmaengine/0 dmaengine/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dmaengine dmaengine/ https://lore.kernel.org/dmaengine \
		dmaengine@vger.kernel.org
	public-inbox-index dmaengine

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.dmaengine


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git