[coreboot] [RFC] [flashrom] "accelerated" high-level external programmer functions and serial external programmer protocol

Urja Rannikko urjaman at gmail.com
Fri Jun 5 23:12:41 CEST 2009

> Yes, for that you need flow control. For example, you you have the
> programmer return the amount of bytes free in the buffer after each
> command stream you send to the device.
For a moment i was adding a "return bytes free in buffer" command to
the protocol, but then i realized that if the code sent that command
as the last in command stream, and waited for the answer, the answer
would always be that the buffer is empty, because it just had to go
though all the data in the buffer to get the command. So i'm sticking
with the
- query buffer size in the beginning
- when doing opbuf writes, count bytes sent
- if about to have sent too many bytes, instead send NOP and wait for
the ACK and clear the counter and continue

I have the protocol specification ready and the AVR code compiles
already, i'm just moving to flashrom code. I'll attach the .txt to
this mail, it's better viewed with proper tabs and fixed-width font
(leafpad fullscreen 1280x1024 is nice :P).

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Serial Flasher Protocol Specification

Command And Answer Sequence - not all commands give an answer
DEV: ACK/NAK(8bit) <OPTIONAL RETURN BYTES (only if ACK)> or nothing

ACK = 0xAA
NAK = 0x55

All multibyte values are little-endian.

COMMAND	Description			Parameters			Return Value
0x00	NOP				none				ACK
0x01	Query serial buffer size	none				ACK + 16bit size / NAK
0x02	Query supported bustypes	none				ACK + 8-bit flags (as per flashrom) / NAK:
									bit 0: PARALLEL
									bit 1: LPC
									bit 2: FWH
									bit 3: SPI if ever supported
0x03	Query supported chip size	none				ACK + 8bit power of two / NAK
0x04	Query operation buffer size	none				ACK + 16bit size / NAK
0x05	Read byte			24-bit addr			ACK + BYTE / NAK
0x06	Read n bytes			24-bit addr + 24-bit lenght	ACK + lenght bytes / NAK
0x07	Initialize operation buffer	none				ACK / NAK
0x08	Write to opbuf: Write byte	24-bit addr + 8-bit byte	nothing	/ NAK (NOTE: takes 6 bytes in opbuf)
0x09	Write to opbuf: Write byte seq	8-bit byte			nothing / NAK (NOTE: takes 1 bytes in opbuf)
0x0A	Write to opbuf: delay		32-bit usecs			nothing / NAK (NOTE: takes 5 bytes in opbuf)
0x0B	Execute operation buffer	none				ACK / NAK 
		- Execute operation buffer will also clear it
0x??	unimplemented command		any				NAK

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