[U-Boot] [PATCH 2/2] mtd: nand: mxc_nand: Fix is_16bit_nand()

[Fabio Estevam]

Currently is_16bit_nand() is a per SoC function and it decides the bus nand 
width by reading some boot related registers.

This method works when NAND is the boot medium, but does not work if another
boot medium is used. For example: booting from a SD card and then using NAND
to store the environment variables, would lead to the following error:

NAND bus width 16 instead 8 bit
No NAND device found!!!
0 MiB

Use CONFIG_SYS_NAND_BUSWIDTH_16BIT symbol to decide the bus width.

If it is defined in the board file, then consider 16-bit NAND bus-width, 
otherwise assume 8-bit NAND is used.

This also aligns with Documentation/devicetree/bindings/mtd/nand.txt, which
states:

nand-bus-width : 8 or 16 bus width if not present 8

Signed-off-by: Fabio Estevam <fabio.estevam at freescale.com>
---
 drivers/mtd/nand/mxc_nand.c |   37 +++----------------------------------
 1 file changed, 3 insertions(+), 34 deletions(-)

diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
index d0ded48..bb475f2 100644
--- a/drivers/mtd/nand/mxc_nand.c
+++ b/drivers/mtd/nand/mxc_nand.c
@@ -98,45 +98,14 @@ static struct nand_ecclayout nand_hw_eccoob2k = {
 #endif
 #endif
 
-#ifdef CONFIG_MX27
 static int is_16bit_nand(void)
 {
-	struct system_control_regs *sc_regs =
-		(struct system_control_regs *)IMX_SYSTEM_CTL_BASE;
-
-	if (readl(&sc_regs->fmcr) & NF_16BIT_SEL)
-		return 1;
-	else
-		return 0;
-}
-#elif defined(CONFIG_MX31)
-static int is_16bit_nand(void)
-{
-	struct clock_control_regs *sc_regs =
-		(struct clock_control_regs *)CCM_BASE;
-
-	if (readl(&sc_regs->rcsr) & CCM_RCSR_NF16B)
-		return 1;
-	else
-		return 0;
-}
-#elif defined(CONFIG_MX25) || defined(CONFIG_MX35)
-static int is_16bit_nand(void)
-{
-	struct ccm_regs *ccm = (struct ccm_regs *)IMX_CCM_BASE;
-
-	if (readl(&ccm->rcsr) & CCM_RCSR_NF_16BIT_SEL)
-		return 1;
-	else
-		return 0;
-}
+#if defined(CONFIG_SYS_NAND_BUSWIDTH_16BIT)
+	return 1;
 #else
-#warning "8/16 bit NAND autodetection not supported"
-static int is_16bit_nand(void)
-{
 	return 0;
-}
 #endif
+}
 
 static uint32_t *mxc_nand_memcpy32(uint32_t *dest, uint32_t *source, size_t size)
 {
-- 
1.7.9.5