u-boot版本是2013.01.01 ，NAND Flash 原理图如下，
在MLO阶段，代码运行到 写寄存器时卡死
void gpmc_init(void)
{
/* putting a blanket check on GPMC based on ZeBu for now */
gpmc_cfg = (struct gpmc *)GPMC_BASE;
#if defined(CONFIG_CMD_NAND) || defined(CONFIG_NOR)
const u32 *gpmc_config = NULL;
u32 base = 0;
u32 size = 0;
#endif
/* global settings */
writel(0x00000008, &gpmc_cfg->sysconfig); // 此处卡死
#ifdef CONFIG_NOR
writel(0x00000000, &gpmc_cfg->irqstatus);
writel(0x00000000, &gpmc_cfg->irqenable);
writel(0x00000A00, &gpmc_cfg->config);
#else
writel(0x00000100, &gpmc_cfg->irqstatus);
writel(0x00000200, &gpmc_cfg->irqenable);
writel(0x00000012, &gpmc_cfg->config);
#endif
///////////////////////////////////////////////////////////////
static struct module_pin_mux nand_pin_mux[] = {
{OFFSET(gpmc_ad0), (MODE(0) | PULLUP_EN | RXACTIVE)}, /* NAND AD0 */
{OFFSET(gpmc_ad1), (MODE(0) | PULLUP_EN | RXACTIVE)}, /* NAND AD1 */
{OFFSET(gpmc_ad2), (MODE(0) | PULLUP_EN | RXACTIVE)}, /* NAND AD2 */
{OFFSET(gpmc_ad3), (MODE(0) | PULLUP_EN | RXACTIVE)}, /* NAND AD3 */
{OFFSET(gpmc_ad4), (MODE(0) | PULLUP_EN | RXACTIVE)}, /* NAND AD4 */
{OFFSET(gpmc_ad5), (MODE(0) | PULLUP_EN | RXACTIVE)}, /* NAND AD5 */
{OFFSET(gpmc_ad6), (MODE(0) | PULLUP_EN | RXACTIVE)}, /* NAND AD6 */
{OFFSET(gpmc_ad7), (MODE(0) | PULLUP_EN | RXACTIVE)}, /* NAND AD7 */
{OFFSET(gpmc_clk), (MODE(2) | RXACTIVE | PULLUP_EN)}, /* NAND WAIT */ //此处配置wait1
{OFFSET(gpmc_wpn), (MODE(0) | PULLUDEN | RXACTIVE)}, /* NAND_WPN */
{OFFSET(gpmc_csn0), (MODE(0) | PULLUDEN)}, /* NAND_CS0 */
{OFFSET(gpmc_advn_ale), (MODE(0) | PULLUDEN)}, /* NAND_ADV_ALE */
{OFFSET(gpmc_oen_ren), (MODE(0) | PULLUDEN)}, /* NAND_OE */
{OFFSET(gpmc_wen), (MODE(0) | PULLUDEN)}, /* NAND_WEN */
{OFFSET(gpmc_be0n_cle), (MODE(0) | PULLUDEN)}, /* NAND_BE_CLE */
{-1},
};
