[PATCH AUTOSEL 5.2 11/85] dmaengine: tegra-apb: Error out if DMA_PREP_INTERRUPT flag is unset

[PATCH AUTOSEL 5.2 11/85] dmaengine: tegra-apb: Error out if DMA_PREP_INTERRUPT flag is unset

[Sasha Levin]

From: Dmitry Osipenko <digetx@gmail.com>

[ Upstream commit dc161064beb83c668e0f85766b92b1e7ed186e58 ]

Apparently driver was never tested with DMA_PREP_INTERRUPT flag being
unset since it completely disables interrupt handling instead of skipping
the callbacks invocations, hence putting channel into unusable state.

The flag is always set by all of kernel drivers that use APB DMA, so let's
error out in otherwise case for consistency. It won't be difficult to
support that case properly if ever will be needed.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/dma/tegra20-apb-dma.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index ef317c90fbe1..79e9593815f1 100644
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -977,8 +977,12 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_slave_sg(
 		csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
 	}
 
-	if (flags & DMA_PREP_INTERRUPT)
+	if (flags & DMA_PREP_INTERRUPT) {
 		csr |= TEGRA_APBDMA_CSR_IE_EOC;
+	} else {
+		WARN_ON_ONCE(1);
+		return NULL;
+	}
 
 	apb_seq |= TEGRA_APBDMA_APBSEQ_WRAP_WORD_1;
 
@@ -1120,8 +1124,12 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_dma_cyclic(
 		csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
 	}
 
-	if (flags & DMA_PREP_INTERRUPT)
+	if (flags & DMA_PREP_INTERRUPT) {
 		csr |= TEGRA_APBDMA_CSR_IE_EOC;
+	} else {
+		WARN_ON_ONCE(1);
+		return NULL;
+	}
 
 	apb_seq |= TEGRA_APBDMA_APBSEQ_WRAP_WORD_1;
 
-- 
2.20.1

[PATCH AUTOSEL 5.2 20/85] dmaengine: rcar-dmac: Reject zero-length slave DMA requests

[Sasha Levin]

From: Geert Uytterhoeven <geert+renesas@glider.be>

[ 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 33ab1b607e2b..54de669c38b8 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1165,7 +1165,7 @@ rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
 
 	/* 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);
-- 
2.20.1