Hello.
While porting U-Boot to a custom board, I faced a situation when U-Boot failed to write of erase to the board flash chip.
Flash chip is SG29GL32M10FAIR4 from Spansion, http://www.spansion.com/products/S29GL032A.html This is CFI-compatible NOR flash chip, that could be used both with 8-bit and 16-bit data bus, selected by hardware setup. In my case, it's in 8-bit mode.
With linux MTD subsystem, write and erase work as expected. Here is what Linux drivers print about the chip when in verbose mode:
physmap flash device: 400000 at 18000000 Number of erase regions: 2 Primary Vendor Command Set: 0002 (AMD/Fujitsu Standard) Primary Algorithm Table at 0040 Alternative Vendor Command Set: 0000 (None) No Alternate Algorithm Table Vcc Minimum: 2.7 V Vcc Maximum: 3.6 V No Vpp line Typical byte/word write timeout: 128 ╣s Maximum byte/word write timeout: 256 ╣s Typical full buffer write timeout: 128 ╣s Maximum full buffer write timeout: 4096 ╣s Typical block erase timeout: 1024 ms Maximum block erase timeout: 16384 ms Chip erase not supported Device size: 0x400000 bytes (4 MiB) Flash Device Interface description: 0x0002 - supports x8 and x16 via BYTE# with asynchronous interface Max. bytes in buffer write: 0x20 Number of Erase Block Regions: 2 Erase Region #0: BlockSize 0x2000 bytes, 8 blocks Erase Region #1: BlockSize 0x10000 bytes, 63 blocks phys_mapped_flash: Found 1 x16 devices at 0x0 in 8-bit bank Amd/Fujitsu Extended Query Table at 0x0040 number of CFI chips: 1 cfi_cmdset_0002: Disabling erase-suspend-program due to code brokenness.
I examined u-boot CFI flash driver code, and the chip datasheet. Looks like u-boot driver defines offsets at which commands are written to the flash as constants, while flash datasheet states the addresses are different in 8bit and 16bit modes.
I was able to make write and erase work by applying the following patch:
diff --git a/drivers/cfi_flash.c b/drivers/cfi_flash.c index 4b7a110..292bda7 100644 --- a/drivers/cfi_flash.c +++ b/drivers/cfi_flash.c @@ -107,9 +107,15 @@
#define AMD_STATUS_TOGGLE 0x40 #define AMD_STATUS_ERROR 0x20 +#ifndef CONFIG_AMD_8BIT_FLASH #define AMD_ADDR_ERASE_START 0x555 #define AMD_ADDR_START 0x555 #define AMD_ADDR_ACK 0x2AA +#else +#define AMD_ADDR_ERASE_START 0xAAA +#define AMD_ADDR_START 0xAAA +#define AMD_ADDR_ACK 0x555 +#endif
#define FLASH_OFFSET_CFI 0x55 #define FLASH_OFFSET_CFI_RESP 0x10
and defining CONFIG_AMD_8BIT_FLASH in my board config file.
I don't know if this is specific to the chip used, or for all chips with AMD command set that work in 8bit mode. If later, maybe it's better to fix the driver to automatically use valid addresses depending on width of the data bus.
Nikita