Commit fc7be630 authored Aug 29, 2018 by Daniel Silsby Committed by Greg Kroah-Hartman Nov 20, 2019

dmaengine: dma-jz4780: Further residue status fix



[ 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>

parent f6d4561c

drivers/dma/dma-jz4780.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -587,7 +587,7 @@ 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;