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

>> 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 <fengguang.wu@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/drivers/dma/sh/shdma-base.c b/drivers/dma/sh/shdma-base.c
index 591b9d8..b35007e 100644 (file)
--- a/drivers/dma/sh/shdma-base.c
+++ b/drivers/dma/sh/shdma-base.c
@@ -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,