Hi
> 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@xxxxxxxxxxxxxxxx>
> ---
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>
> drivers/dma/sh/shdma-base.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
>
> Morimoto-san, would you be able to test this change with the audio driver ? I
> believe it's our only user of cyclic transfers.
>
> diff --git a/drivers/dma/sh/shdma-base.c b/drivers/dma/sh/shdma-base.c
> index 94b6bde..e427a03 100644
> --- a/drivers/dma/sh/shdma-base.c
> +++ b/drivers/dma/sh/shdma-base.c
> @@ -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,
> --
> Regards,
>
> Laurent Pinchart
>
> --
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Best regards
---
Kuninori Morimoto
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