[PATCH] mtd: raw: qcom_nand: Fix register write error

[Sivaprakash Murugesan]

1. SFLASHC_BURST_CFG register is not available on all ipq nand platforms,
   it is available only on ipq8064 devices and the nand controller works
   without configuring these registers in this platform, so register
   write to this can be removed.

2. Once BAM mode is enabled register writes to NAND_CTRL should be
   performed through BAM command descriptors. The NAND BAM mode will
   be enabled by bootloaders. Check if BAM mode is already enabled and
   enable it only if not enabled already.

Signed-off-by: Sivaprakash Murugesan <sivaprak@xxxxxxxxxxxxxx>
---
 drivers/mtd/nand/raw/qcom_nandc.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
index 5b11c70..7bfd93a 100644
--- a/drivers/mtd/nand/raw/qcom_nandc.c
+++ b/drivers/mtd/nand/raw/qcom_nandc.c
@@ -36,7 +36,6 @@
 #define	NAND_DEV_CMD1			0xa4
 #define	NAND_DEV_CMD2			0xa8
 #define	NAND_DEV_CMD_VLD		0xac
-#define	SFLASHC_BURST_CFG		0xe0
 #define	NAND_ERASED_CW_DETECT_CFG	0xe8
 #define	NAND_ERASED_CW_DETECT_STATUS	0xec
 #define	NAND_EBI2_ECC_BUF_CFG		0xf0
@@ -2774,14 +2773,20 @@ static int qcom_nandc_setup(struct qcom_nand_controller *nandc)
 	u32 nand_ctrl;
 
 	/* kill onenand */
-	nandc_write(nandc, SFLASHC_BURST_CFG, 0);
 	nandc_write(nandc, dev_cmd_reg_addr(nandc, NAND_DEV_CMD_VLD),
 		    NAND_DEV_CMD_VLD_VAL);
 
 	/* enable ADM or BAM DMA */
 	if (nandc->props->is_bam) {
 		nand_ctrl = nandc_read(nandc, NAND_CTRL);
-		nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN);
+		/* Once BAM_MODE_EN bit is set, writes to the NAND_CTRL
+		 * should be done through BAM command descriptors.
+		 * in most cases bootloader enables the bam mode we
+		 * need to set the BAM mode only if it is not set by
+		 * bootloader
+		 */
+		if (!(nand_ctrl & BAM_MODE_EN))
+			nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN);
 	} else {
 		nandc_write(nandc, NAND_FLASH_CHIP_SELECT, DM_EN);
 	}
-- 
2.7.4