Staging: goldfish: goldfish_nand: Add DMA Support using dmam_alloc_coherent

Function nand_setup_cmd_params has 2 goals-

-Initialize the cmd_params field so that it can be used to send and read
commands from the device.
-Get a bus address for the allocated memory to transfer to the device.

Replace the combination of devm_kzalloc and _pa() with dmam_alloc_coherent.
Coherent mapping guarantees that the device and CPU are in sync.
Signed-off-by: Shraddha Barke <shraddha.6596@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/goldfish/goldfish_nand.c

@@ -27,6 +27,7 @@
 #include <linux/mutex.h>
 #include <linux/goldfish.h>
 #include <asm/div64.h>
+#include <linux/dma-mapping.h>
 
 #include "goldfish_nand_reg.h"
 
@@ -284,17 +285,18 @@ static int goldfish_nand_block_markbad(struct mtd_info *mtd, loff_t ofs)
 static int nand_setup_cmd_params(struct platform_device *pdev,
 				 struct goldfish_nand *nand)
 {
-	u64 paddr;
+	dma_addr_t dma_handle;
 	unsigned char __iomem  *base = nand->base;
 
-	nand->cmd_params = devm_kzalloc(&pdev->dev,
-					sizeof(struct cmd_params), GFP_KERNEL);
-	if (!nand->cmd_params)
-		return -1;
-
-	paddr = __pa(nand->cmd_params);
-	writel((u32)(paddr >> 32), base + NAND_CMD_PARAMS_ADDR_HIGH);
-	writel((u32)paddr, base + NAND_CMD_PARAMS_ADDR_LOW);
+	nand->cmd_params = dmam_alloc_coherent(&pdev->dev,
+					       sizeof(struct cmd_params),
+					       &dma_handle, GFP_KERNEL);
+	if (!nand->cmd_params) {
+		dev_err(&pdev->dev, "allocate buffer failed\n");
+		return -ENOMEM;
+	}
+	writel((u32)((u64)dma_handle >> 32), base + NAND_CMD_PARAMS_ADDR_HIGH);
+	writel((u32)dma_handle, base + NAND_CMD_PARAMS_ADDR_LOW);
 	return 0;
 }