spi: spi-qcom-qspi: Use GFP_ATOMIC flag while allocating for descriptor

While allocating for DMA descriptor, GFP_KERNEL flag is being used and
this allocation happens within critical section with spinlock acquired.
This generates a static checker warning.

Use GFP_ATOMIC to prevent sleeping; and since this increases chances of
allocation failure, add handling accordingly.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/abc223e8-44af-40bb-a0bd-9865b393f435@moroto.mountain/
Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
Fixes: b5762d9 ("spi: spi-qcom-qspi: Add DMA mode support")
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/1690285689-30233-3-git-send-email-quic_vnivarth@quicinc.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Vijaya Krishna Nivarthi

drivers/spi/spi-qcom-qspi.c

@@ -308,9 +308,11 @@ static int qcom_qspi_alloc_desc(struct qcom_qspi *ctrl, dma_addr_t dma_ptr,
 	dma_addr_t dma_cmd_desc;
 
 	/* allocate for dma cmd descriptor */
-	virt_cmd_desc = dma_pool_alloc(ctrl->dma_cmd_pool, GFP_KERNEL | __GFP_ZERO, &dma_cmd_desc);
-	if (!virt_cmd_desc)
-		return -ENOMEM;
+	virt_cmd_desc = dma_pool_alloc(ctrl->dma_cmd_pool, GFP_ATOMIC | __GFP_ZERO, &dma_cmd_desc);
+	if (!virt_cmd_desc) {
+		dev_warn_once(ctrl->dev, "Couldn't find memory for descriptor\n");
+		return -EAGAIN;
+	}
 
 	ctrl->virt_cmd_desc[ctrl->n_cmd_desc] = virt_cmd_desc;
 	ctrl->dma_cmd_desc[ctrl->n_cmd_desc] = dma_cmd_desc;