官网上是这样的
sunxi-fel增加对16M以上Flash的支持

由于SPI flash 的地址是24bit，也就是最大16M 地址空间，所以对于32M flash，需要增加bank切换支持。
uboot中有 CONFIG_SPI_FLASH_BAR 选项可以使能bank切换。
但是sunxi-fel中尚未支持，所以下载的时候超出16M会循环覆盖掉。
这里介绍对sunxi-fel增加16M以上flash支持的方法。
u-boot的支持
drivers/mtd/spi/spi_flash.c
static int write_bar(struct spi_flash *flash, u32 offset)
{
u8 cmd, bank_sel;
int ret;

bank_sel = offset / (SPI_FLASH_16MB_BOUN << flash->shift);
if (bank_sel == flash->bank_curr)
goto bar_end;

cmd = flash->bank_write_cmd;
ret = spi_flash_write_common(flash, &cmd, 1, &bank_sel, 1);
if (ret < 0) {
debug("SF: fail to write bank register\n");
return ret;
}

bar_end:
flash->bank_curr = bank_sel;
return flash->bank_curr;
}
sunxi-fel的支持
fel-spiflash.c
#define CMD_WRITE_ENABLE 0x06
#define SPI_FLASH_16MB_BOUN 0x1000000

define CMD_BANKADDR_BRWR 0x17 //only SPANSION flash use it

define CMD_BANKADDR_BRRD 0x16

define CMD_EXTNADDR_WREAR 0xC5

define CMD_EXTNADDR_RDEAR 0xC8

size_t bank_curr = 0;

void aw_fel_spiflash_write_helper(feldev_handle *dev,
uint32_t offset, void *buf, size_t len,
size_t erase_size, uint8_t erase_cmd,
size_t program_size, uint8_t program_cmd)
{
uint8_t buf8 = (uint8_t )buf;
size_t max_chunk_size = dev->soc_info->scratch_addr - dev->soc_info->spl_addr;
size_t cmd_idx, bank_sel;

if (max_chunk_size > 0x1000)
max_chunk_size = 0x1000;
uint8_t *cmdbuf = malloc(max_chunk_size);
cmd_idx = 0;

prepare_spi_batch_data_transfer(dev, dev->soc_info->spl_addr);
//add bank support
{
cmd_idx = 0;
bank_sel = offset /SPI_FLASH_16MB_BOUN;
if (bank_sel == bank_curr)
goto bar_end;

/ Emit write enable command /
cmdbuf[cmd_idx++] = 0;
cmdbuf[cmd_idx++] = 1;
cmdbuf[cmd_idx++] = CMD_WRITE_ENABLE;
/ Emit write bank /
cmdbuf[cmd_idx++] = 0;
cmdbuf[cmd_idx++] = 2;
cmdbuf[cmd_idx++] = CMD_EXTNADDR_WREAR;
cmdbuf[cmd_idx++] = offset >> 24;
/ Emit wait for completion /
cmdbuf[cmd_idx++] = 0xFF;
cmdbuf[cmd_idx++] = 0xFF;
/ Emit the end marker /
cmdbuf[cmd_idx++] = 0;
cmdbuf[cmd_idx++] = 0;
aw_fel_write(dev, cmdbuf, dev->soc_info->spl_addr, cmd_idx);
aw_fel_remotefunc_execute(dev, NULL);
bar_end:
bank_curr = bank_sel;
}

cmd_idx = 0;
重新编译sunxi-fel后就可以烧录32M flash了~