[ Upstream commit 78efb76ab4dfb8f74f290ae743f34162cd627f19 ]
While the .device_prep_slave_sg() callback rejects empty scatterlists, it still accepts single-entry scatterlists with a zero-length segment. These may happen if a driver calls dmaengine_prep_slave_single() with a zero len parameter. The corresponding DMA request will never complete, leading to messages like:
rcar-dmac e7300000.dma-controller: Channel Address Error happen
and DMA timeouts.
Although requesting a zero-length DMA request is a driver bug, rejecting it early eases debugging. Note that the .device_prep_dma_memcpy() callback already rejects requests to copy zero bytes.
Reported-by: Eugeniu Rosca erosca@de.adit-jv.com Analyzed-by: Yoshihiro Shimoda yoshihiro.shimoda.uh@renesas.com Signed-off-by: Geert Uytterhoeven geert+renesas@glider.be Signed-off-by: Vinod Koul vkoul@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/dma/sh/rcar-dmac.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c index 2b36d1c63aa5f..956189a1ba81c 100644 --- a/drivers/dma/sh/rcar-dmac.c +++ b/drivers/dma/sh/rcar-dmac.c @@ -1030,7 +1030,7 @@ rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl, dma_addr_t dev_addr;
/* Someone calling slave DMA on a generic channel? */ - if (rchan->mid_rid < 0 || !sg_len) { + if (rchan->mid_rid < 0 || !sg_len || !sg_dma_len(sgl)) { dev_warn(chan->device->dev, "%s: bad parameter: len=%d, id=%d\n", __func__, sg_len, rchan->mid_rid);