dmaengine: shdma: Allocate cyclic sg list dynamically (4415b03a) · Commits · 戴 / test

The sg list used to prepare cyclic DMA descriptors is currently allocated statically on the stack as an array of 32 elements. This makes the shdma_prep_dma_cyclic() function consume a lot of stack space, as reported by the compiler: drivers/dma/sh/shdma-base.c: In function ‘shdma_prep_dma_cyclic’: drivers/dma/sh/shdma-base.c:715:1: warning: the frame size of 1056 bytes is larger than 1024 bytes [-Wframe-larger-than=] Given the limited Linux kernel stack size, this could lead to stack overflows. Fix the problem by allocating the sg list dynamically. Signed-off-by:

Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> Signed-off-by:

Simon Horman <horms+renesas@verge.net.au> Signed-off-by:

Vinod Koul <vinod.koul@intel.com>

drivers/dma/sh/shdma-base.c

+15 −2

Original line number	Diff line number	Diff line
		@@ -672,11 +672,12 @@ static struct dma_async_tx_descriptor *shdma_prep_dma_cyclic(
		{
		struct shdma_chan *schan = to_shdma_chan(chan);
		struct shdma_dev *sdev = to_shdma_dev(schan->dma_chan.device);
		struct dma_async_tx_descriptor *desc;
		const struct shdma_ops *ops = sdev->ops;
		unsigned int sg_len = buf_len / period_len;
		int slave_id = schan->slave_id;
		dma_addr_t slave_addr;
		struct scatterlist sgl[SHDMA_MAX_SG_LEN];
		struct scatterlist *sgl;
		int i;

		if (!chan)
		@@ -700,7 +701,16 @@ static struct dma_async_tx_descriptor *shdma_prep_dma_cyclic(

		slave_addr = ops->slave_addr(schan);

		/*
		* Allocate the sg list dynamically as it would consumer too much stack
		* space.
		*/
		sgl = kcalloc(sg_len, sizeof(*sgl), GFP_KERNEL);
		if (!sgl)
		return NULL;

		sg_init_table(sgl, sg_len);

		for (i = 0; i < sg_len; i++) {
		dma_addr_t src = buf_addr + (period_len * i);

		@@ -710,8 +720,11 @@ static struct dma_async_tx_descriptor *shdma_prep_dma_cyclic(
		sg_dma_len(&sgl[i]) = period_len;
		}

		return shdma_prep_sg(schan, sgl, sg_len, &slave_addr,
		desc = shdma_prep_sg(schan, sgl, sg_len, &slave_addr,
		direction, flags, true);

		kfree(sgl);
		return desc;
		}

		static int shdma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,

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