[people/ms/u-boot.git] / doc / README.cfi

The common CFI driver provides this weak default implementation for
flash_cmd_reset():

void __flash_cmd_reset(flash_info_t *info)
{
	/*
	 * We do not yet know what kind of commandset to use, so we issue
	 * the reset command in both Intel and AMD variants, in the hope
	 * that AMD flash roms ignore the Intel command.
	 */
	flash_write_cmd(info, 0, 0, AMD_CMD_RESET);
	flash_write_cmd(info, 0, 0, FLASH_CMD_RESET);
}
void flash_cmd_reset(flash_info_t *info)
	__attribute__((weak,alias("__flash_cmd_reset")));


Some flash chips seems to have trouble with this reset sequence. In this case
the board specific code can override this weak default version with a board
specific function. For example the digsy_mtc board equipped with the M29W128GH
from Numonyx needs this version to function properly:

void flash_cmd_reset(flash_info_t *info)
{
	flash_write_cmd(info, 0, 0, AMD_CMD_RESET);
}

see also:
http://www.mail-archive.com/u-boot@lists.denx.de/msg24368.html
Commit	Line	Data
466f0137 HS	1	The common CFI driver provides this weak default implementation for
	2	flash_cmd_reset():
	3
	4	void __flash_cmd_reset(flash_info_t *info)
	5	{
	6	/*
	7	* We do not yet know what kind of commandset to use, so we issue
	8	* the reset command in both Intel and AMD variants, in the hope
	9	* that AMD flash roms ignore the Intel command.
	10	*/
	11	flash_write_cmd(info, 0, 0, AMD_CMD_RESET);
	12	flash_write_cmd(info, 0, 0, FLASH_CMD_RESET);
	13	}
	14	void flash_cmd_reset(flash_info_t *info)
	15	__attribute__((weak,alias("__flash_cmd_reset")));
	16
	17
	18	Some flash chips seems to have trouble with this reset sequence. In this case
	19	the board specific code can override this weak default version with a board
	20	specific function. For example the digsy_mtc board equipped with the M29W128GH
	21	from Numonyx needs this version to function properly:
	22
	23	void flash_cmd_reset(flash_info_t *info)
	24	{
	25	flash_write_cmd(info, 0, 0, AMD_CMD_RESET);
	26	}
	27
	28	see also:
	29	http://www.mail-archive.com/u-boot@lists.denx.de/msg24368.html