Jonathan Haws wrote:

Okay, I now have access to the flash memory, however when I write to it the writes do not take.  I have tried calling msync() on the mapping to no avail.  I have opened the fd with O_SYNC, but cannot get things to work right.

Here are the calls:

	int fd = open("/dev/mem", O_SYNC | O_RDWR);
	uint16_t * flash = (uint16_t *)mmap(NULL, NOR_FLASH_SIZE,
			(PROT_READ | PROT_WRITE), MAP_PRIVATE, fd,
			NOR_FLASH_BASE_ADRS);

When I do flash[0] = 0x1234, and then check the value, they do not match.

	flash[0] = 0x1234;
	msync(flash, NOR_FLASH_SIZE, MS_SYNC | MS_INVALIDATE);
	printf("flash[0] = %#04x\n", flash[0]);

That prints flash[0] = 0x7f45.  I have verified that I am reading the correct values.  I can display the flash contents in U-Boot and 7f45 is what is in the first 16 bits of flash.

Why can I not write to flash?  What am I doing wrong?

Flash does not work that way -- you must send it commands to erase a 
block, and then further commands to program new data.

It sounds like what you really want is the /dev/mtd or /dev/mtdblock 
interface, not raw access to the flash chip.

-Scott