6. 移植u-boot-2016.03修改代码支持NAND Flash
从前面串口的打印信息可知，uboot并没有识别出NAND Flash空间的大小，显示：NAND: 0 MiB，如下图所示：
6.1 分析u-boot-2016.03源码之NAND Flash
我们在uboot的顶层目录输入命令：grep -nR "NAND:"，在common/board_r.c中的432行有如下代码：
#ifdef CONFIG_CMD_NAND
/* go init the NAND */
static int initr_nand(void)
{
puts("NAND: ");
nand_init();
return 0;
}
#endif
其中，CONFIG_CMD_NAND在jz2440.h被定义，initr_nand函数在uboot进行第二阶段初始化时被board_init_r函数调用。nand_init函数被board_init_r函数调用，nand_init函数的代码如下：(该函数在drivers/mtd/nand/nand.c)
void nand_init(void)
{
#ifdef CONFIG_SYS_NAND_SELF_INIT /*未定义*/
board_nand_init();
#else
int i;
for (i = 0; i < CONFIG_SYS_MAX_NAND_DEVICE; i++)
nand_init_chip(i);
#endif
printf("%lu MiB\n", total_nand_size / 1024);
#ifdef CONFIG_SYS_NAND_SELECT_DEVICE
/*
* Select the chip in the board/cpu specific driver
*/
board_nand_select_device(nand_info[nand_curr_device].priv, nand_curr_device);
#endif
}
关于上面代码#ifdef CONFIG_SYS_NAND_SELF_INIT中的CONFIG_SYS_NAND_SELF_INIT，在nand.h中的代码如下图所示：(source insight截图)，从图可知CONFIG_SPL_BUILD是黑色的，说明没有定义；因此，上面的代码不会执行board_nand_init()函数。
跳过board_nand_init()函数，执行nand_init_chip()函数：
static void nand_init_chip(int i)
{
struct mtd_info *mtd = &nand_info[i];
struct nand_chip *nand = &nand_chip[i];
ulong base_addr = base_address[i];
int maxchips = CONFIG_SYS_NAND_MAX_CHIPS;
if (maxchips < 1)
maxchips = 1;
mtd->priv = nand;
nand->IO_ADDR_R = nand->IO_ADDR_W = (void __iomem *)base_addr;
if (board_nand_init(nand))
return;
if (nand_scan(mtd, maxchips))
return;
nand_register(i);
}
接下来看board_nand_init函数：(在drivers/mtd/nand/s3c2410_nand.c)
int board_nand_init(struct nand_chip *nand)
{
u_int32_t cfg;
u_int8_t tacls, twrph0, twrph1;
struct s3c24x0_clock_power *clk_power = s3c24x0_get_base_clock_power();
struct s3c24x0_nand *nand_reg = s3c24x0_get_base_nand();
debug("board_nand_init()\n");
writel(readl(&clk_power->clkcon) | (1 << 4), &clk_power->clkcon);
/* initialize hardware */
#if defined(CONFIG_S3C24XX_CUSTOM_NAND_TIMING)
tacls = CONFIG_S3C24XX_TACLS;
twrph0 = CONFIG_S3C24XX_TWRPH0;
twrph1 = CONFIG_S3C24XX_TWRPH1;
#else
tacls = 4;
twrph0 = 8;
twrph1 = 8;
#endif
cfg = S3C2410_NFCONF_EN;
cfg |= S3C2410_NFCONF_TACLS(tacls - 1);
cfg |= S3C2410_NFCONF_TWRPH0(twrph0 - 1);
cfg |= S3C2410_NFCONF_TWRPH1(twrph1 - 1);
writel(cfg, &nand_reg->nfconf);
/* initialize nand_chip data structure */
nand->IO_ADDR_R = (void *)&nand_reg->nfdata;
nand->IO_ADDR_W = (void *)&nand_reg->nfdata;
nand->select_chip = NULL;
/* read_buf and write_buf are default */
/* read_byte and write_byte are default */
#ifdef CONFIG_NAND_SPL
nand->read_buf = nand_read_buf;
#endif
/* hwcontrol always must be implemented */
nand->cmd_ctrl = s3c24x0_hwcontrol;
nand->dev_ready = s3c24x0_dev_ready;
#ifdef CONFIG_S3C2410_NAND_HWECC
nand->ecc.hwctl = s3c24x0_nand_enable_hwecc;
nand->ecc.calculate = s3c24x0_nand_calculate_ecc;
nand->ecc.correct = s3c24x0_nand_correct_data;
nand->ecc.mode = NAND_ECC_HW;
nand->ecc.size = CONFIG_SYS_NAND_ECCSIZE;
nand->ecc.bytes = CONFIG_SYS_NAND_ECCBYTES;
nand->ecc.strength = 1;
#else
nand->ecc.mode = NAND_ECC_SOFT;
#endif
#ifdef CONFIG_S3C2410_NAND_BBT
nand->bbt_options |= NAND_BBT_USE_FLASH;
#endif
debug("end of nand_init\n");
return 0;
}
通过分析上面的代码，发现设置时序的时候，与2440手册对比发现，发现时序设置不对，它是适用于2410的，并不适用于2440，设置时序的代码如下：
cfg |= S3C2440_NFCONF_TACLS(tacls - 1);
cfg |= S3C2440_NFCONF_TWRPH0(twrph0 - 1);
cfg |= S3C2440_NFCONF_TWRPH1(twrph1 - 1);
writel(cfg, &nand_reg->nfconf);
接下来是s3c24x0_hwcontrol函数，它的代码如下：
static void s3c24x0_hwcontrol(struct mtd_info *mtd, int cmd, unsigned int ctrl)
{
struct nand_chip *chip = mtd->priv;
struct s3c24x0_nand *nand = s3c24x0_get_base_nand();
debug("hwcontrol(): 0x%02x 0x%02x\n", cmd, ctrl);
if (ctrl & NAND_CTRL_CHANGE) {
ulong IO_ADDR_W = (ulong)nand;
if (!(ctrl & NAND_CLE))
IO_ADDR_W |= S3C2410_ADDR_NCLE;
if (!(ctrl & NAND_ALE))
IO_ADDR_W |= S3C2410_ADDR_NALE;
chip->IO_ADDR_W = (void *)IO_ADDR_W;
if (ctrl & NAND_NCE) /*使能片选*/
writel(readl(&nand->nfconf) & ~S3C2410_NFCONF_nFCE,
&nand->nfconf);
else /*取消片选*/
writel(readl(&nand->nfconf) | S3C2410_NFCONF_nFCE,
&nand->nfconf);
}
if (cmd != NAND_CMD_NONE)
writeb(cmd, chip->IO_ADDR_W);
}
上的代码是2410的配置，我们的Jz2440开发板是2440的，查看2440手册查看相关寄存器发现，对于2440的NAND 片选使能与取消是通过配置NFCONT寄存的**bit[1]**实现的，如下图所示：
6.2 修改代码NAND Flash
(1) 把drivers/mtd/nand/s3c2410_nand.c复制为s3c2440_nand.c；
(2) 修改 drivers/mtd/nand/目录下的Makefile，在Makefile里搜索CONFIG_NAND_S3C2410，有如下代码：
obj-$(CONFIG_NAND_S3C2410) += s3c2410_nand.o
在这行代码后面添加下面的代码，把s3c2440_nand.c编译进uboot；
obj-$(CONFIG_NAND_S3C2440) += s3c2440_nand.o
(3) 在include/configs/jz2440.h中添加支持s3c2440_nand，在jz2440.h中搜索CONFIG_NAND_S3C2410，有如下代码：
修改为：
(4) 把board_nand_init函数的设置NAND 时序部分的代码：
cfg |= S3C2410_NFCONF_TACLS(tacls - 1);
cfg |= S3C2410_NFCONF_TWRPH0(twrph0 - 1);
cfg |= S3C2410_NFCONF_TWRPH1(twrph1 - 1);
writel(cfg, &nand_reg->nfconf);
改为：
/* 初始化时序 */
cfg = ((tacls-1)<<12)|((twrph0-1)<<8)|((twrph1-1)<<4);
writel(cfg, &nand_reg->nfconf);
(5) 修改s3c24x0_hwcontrol函数代码如下：
static void s3c24x0_hwcontrol(struct mtd_info *mtd, int cmd, unsigned int ctrl)
{
struct nand_chip *chip = mtd->priv;
struct s3c24x0_nand *nand = s3c24x0_get_base_nand();
if (ctrl & NAND_CLE)
{
/* 发命令 */
writeb(cmd, &nand->nfcmd);
}
if (ctrl & NAND_ALE)
{
/* 发地址 */
writeb(cmd, &nand->nfaddr);
}
}
(6) 同时还需要在board_nand_init函数里加上nand->select_chip = s3c2440_nand_select;所以，将
nand->select_chip = NULL;
修改为：
nand->select_chip = s3c2440_nand_select;
(7) 添加s3c2440_nand_select函数，代码如下：
static void s3c2440_nand_select(struct mtd_info *mtd, int chipnr)
{
struct s3c24x0_nand *nand = s3c24x0_get_base_nand();
switch (chipnr) {
case -1: /* 取消选中 */
nand->nfcont |= (1<<1);
break;
case 0: /* 选中 */
nand->nfcont &= ~(1<<1);
break;
default:
BUG();
}
}
6.3 测试
(1) 把上面修改好的代码重新编译，然后把u-boot.bin 烧写到开发板的NOR Flash，设置为NOR启动，串口打印信息如下：
从上面打印的信息可知，uboot成功识别出NAND Flash空间的大小。
(2) 下面从NAND Flash启动看看能否识别，首先我们从NOR启动的uboot直接把uboot拷贝到NAND，输入以下命令：
nand erase 0 80000 //擦除NAND flash 的512kB空间
nand write 0 0 80000 //把NOR Flash的前512KB拷贝到 NAND Flash
然后测试烧写到NAND Flash中的uboot是否正常，输入以下命令：
nand read 30000000 0 80000 //把NAND Flash的前512kB读到SDRAM
cmp.b 0 30000000 80000 //比较拷贝的代码是否全部一样
从上图的最后比较结果可知，代码拷贝完全正确。
(3) 然后，设置为NAND Flash启动，并重启开发板，打印结果如下图，从图中可知，成功识别出NAND: 256 MiB
(4) 从上面的测试现象可知，此时的uboot成功支持NAND Flash。