[U-Boot] [PATCH 2/5] imx: mx6sabresd: implement mmc_get_env_devno

[Peng Fan <Peng.Fan@freescale.com>]

Implement mmc_get_env_devno, support loading env successfully
when booting from different slots.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
---
 board/freescale/mx6sabresd/mx6sabresd.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/board/freescale/mx6sabresd/mx6sabresd.c b/board/freescale/mx6sabresd/mx6sabresd.c
index 581c9d5..22ed331 100644
--- a/board/freescale/mx6sabresd/mx6sabresd.c
+++ b/board/freescale/mx6sabresd/mx6sabresd.c
@@ -234,6 +234,35 @@ struct fsl_esdhc_cfg usdhc_cfg[3] = {
 #define USDHC2_CD_GPIO	IMX_GPIO_NR(2, 2)
 #define USDHC3_CD_GPIO	IMX_GPIO_NR(2, 0)
 
+int mmc_get_env_devno(void)
+{
+	struct src *src_regs = (struct src *)SRC_BASE_ADDR;
+	u32 soc_sbmr = readl(&src_regs->sbmr1);
+	u32 dev_no;
+	u32 bootsel;
+
+	/*
+	 * Refer to
+	 * "i.MX 6Dual/6Quad Applications Processor Reference Manual"
+	 * Chapter "8.5.3.1 Expansion Device eFUSE Configuration"
+	 */
+	bootsel = (soc_sbmr & 0x000000FF) >> 6 ;
+
+	/* If not boot from sd/mmc, use default value */
+	if (bootsel != 1)
+		return CONFIG_SYS_MMC_ENV_DEV;
+
+	/* BOOT_CFG2[3] and BOOT_CFG2[4] */
+	dev_no = (soc_sbmr & 0x00001800) >> 11;
+
+	/*
+	 * need ubstract 1 to map to the mmc device id
+	 * see the comments in board_mmc_init function
+	 */
+
+	return --dev_no;
+}
+
 int board_mmc_getcd(struct mmc *mmc)
 {
 	struct fsl_esdhc_cfg *cfg = (struct fsl_esdhc_cfg *)mmc->priv;
-- 
2.6.2