2.4.24-uc0内核移植到44B0X问题集4

john_sagitta

uclinux-2.4.24-uc0支持44B0X开发板----MTD设备的支持

Flash 芯片访问导致中断处理异常。

我使用的是39VF160 Flash芯片，规划是第一块64K保存Bootloader，下面13 * 64K放Kernel，再下面17 * 64K放rootfs（cramfs），最后一块

放nvram。所以我添加了一个MTD MAP文件，drivers/mtd/maps/sample44b0x.c，分区如下：
static struct mtd_partition sample44b0x_partitions[] = {
{
  name: "sample bootloader",
  offset: 0x00000000,
  size: 0x00010000,
     },
{
  name: "sample kenrel",
  offset: 0x00010000,
  size: 0x000d0000,
},
{
  name: "sample rootfs",
  offset: 0x000e0000,
  size: 0x00110000,
},
{
  name: "sample nvram",
  offset: 0x001f0000,
  size: 0x00010000,
},
};

而所遇到的问题是：在Init函数中调用do_map_probe("jedec_probe", &yatech44b0x_map)时，系统当机。原因在与：
Flash 0 地址存放着异常向量表，此时中断已经开启，而jedec_probe需要读取Flash的Manufactory ID & Device ID
读取的过程如下：
enter_sw_id_query_mode();
ManuID = *((u16 *)0);
DevID = *((u16 *)2);
exit_sw_id_query_mode();
也就是说，当39VF160处于ID QUERY MODE时，数据也特殊，这时如果不关中断，就会飞掉。
所以，修改drivers/mtd/chips/jedec_probe.c文件，修改函数jedec_probe_chip()：
......
/* Reset */
jedec_reset(base, map, cfi); // 退出sw_id_query_mode

#ifdef CONFIG_BOARD_SAMPLE44B0X
/* John Added, 'cause our interrupt vectors are installed at address 0
  * By entering SW PID query mode, interrupts must be disabled.
  */
cli();  // 关中断
#endif
/* Autoselect Mode */  // 进入sw_id_query_mode
if(cfi->addr_unlock1) {
  cfi_send_gen_cmd(0xaa, cfi->addr_unlock1, base, map, cfi, CFI_DEVICETYPE_X8, NULL);
  cfi_send_gen_cmd(0x55, cfi->addr_unlock2, base, map, cfi, CFI_DEVICETYPE_X8, NULL);
}
cfi_send_gen_cmd(0x90, cfi->addr_unlock1, base, map, cfi, CFI_DEVICETYPE_X8, NULL);
......
jedec_reset(base, map, cfi); // 退出sw_id_query_mode
......

修改jedec_reset()函数：
static inline void jedec_reset(u32 base, struct map_info *map,
struct cfi_private *cfi)
{
/* Reset */
cfi_send_gen_cmd(0xF0, 0, base, map, cfi, cfi->device_type, NULL);
/* Some misdesigned intel chips do not respond for 0xF0 for a reset,
  * so ensure we're in read mode.  Send both the Intel and the AMD command
  * for this.  Intel uses 0xff for this, AMD uses 0xff for NOP, so
  * this should be safe.
  */
cfi_send_gen_cmd(0xFF, 0, base, map, cfi, cfi->device_type, NULL);
#ifdef CONFIG_BOARD_SAMPLE44B0X
/* John Added, 'cause our interrupt vectors are installed at address 0
  * By entering SW PID query mode, interrupts must be disabled.
  * When return, we re-enable the interrupts.
  */
sti(); // 开中断
#endif
}
这样就解决了这个问题。