dmaengine: sh: don't use dynamic static allocation

dynamic stack allocation in kernel is considered bad as kernel stack is low and we get warns on few archs as reported by kbuild test robot

Quoted 4 lines

Quoted 4 lines

drivers/dma/sh/shdma-base.c:671:32: sparse: Variable length array is used.
drivers/dma/sh/shdma-base.c:701:1: warning: 'shdma_prep_dma_cyclic' uses dynamic stack allocation [enabled by default]

Fix this by making a static array of 32 which should be sufficient for shdma_prep_dma_cyclic which only user in kernel is audio and 32 periods for audio seems quite sufficient atm

Reported-by kbuild test robot <[email protected]>

Signed-off-by Vinod Koul <[email protected]>

---
 drivers/dma/sh/shdma-base.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

drivers/dma/sh/shdma-base.c +9 -1

index 591b9d8..b35007e 100644
@@ -657,6 +657,8 @@ static struct dma_async_tx_descriptor
 *shdma_prep_slave_sg( direction, flags, false);
 }
 
+#define SHDMA_MAX_SG_LEN 32
+
 static struct dma_async_tx_descriptor *shdma_prep_dma_cyclic(
 	struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
 	size_t period_len, enum dma_transfer_direction direction,

@@ -668,7 +670,7 @@ static struct dma_async_tx_descriptor
 *shdma_prep_dma_cyclic( unsigned int sg_len = buf_len / period_len;
 	int slave_id = schan->slave_id;
 	dma_addr_t slave_addr;
-	struct scatterlist sgl[sg_len];
+	struct scatterlist sgl[SHDMA_MAX_SG_LEN];
 	int i;
 
 	if (!chan)

@@ -676,6 +678,12 @@ static struct dma_async_tx_descriptor
 *shdma_prep_dma_cyclic(
 
 	BUG_ON(!schan->desc_num);
 
+	if (sg_len > SHDMA_MAX_SG_LEN) {
+		dev_err(schan->dev, "sg length %d exceds limit %d",
+				sg_len, SHDMA_MAX_SG_LEN);
+		return NULL;
+	}
+
 	/* Someone calling slave DMA on a generic channel? */
 	if (slave_id < 0 || (buf_len < period_len)) {

dev_warn(schan->dev,