[coreboot] Tester devices [was: QA contribution]

[Carl-Daniel Hailfinger]

Hi Juhana,

I've added the flashrom mailing list to CC.

Auf 12.02.2011 19:55, Juhana Helovuo schrieb:
> Now there is more progress. After some building, coding, and debugging
> I have the tester sort-of-working.
>
> The first version of the hardware works.
>
> In this image you can see the tester plugged into an Asus mainboard:
>
> http://alpskari.asiantuntijat.org/~juhe/in-system-flasher/DSC08430.jpg
>
> Today I successfully used this setup to reflash the mainboard from the
> host PC via flashrom.
>
> The USB cable goes to a host computer, which is running a modified
> flashrom program. The flashrom is extended with a serprog_spi module,
> which can transfer SPI over the serprog protocol, and additionally
> toggle SPI bus multiplexer between the MCU and mainboard at the
> beginning and end of programming.
>
> The tester hardware has the following features:
>
> * Tester can access the ROM also when disconnected from the target
> mainboard.
>
> The work is still quite incomplete:
>
> * Currently there is no tester firmware that could operate both the
> SPI and RS-232. The main problem is that the AT90USB162
> microcontroller supports only up to five USB endpoints (including
> default control EP). I do not know if it is possible to implement two
> USB CDC class virtual serial ports with less than seven EPs. With two
> serial ports, one could represent the RS-232 interface, and other be
> used to control the programmer without writing any custom USB drivers.
>
> This could be solved either in software by writing a custom USB driver
> for both the tester and the host, or in hardware by replacing the
> microcontroller with a more capable model. If anyone on the list can
> suggest any easier solutions, I'd be glad to hear about them.
>
> * The handling of SPI ROM is horribly slow. Programming and verifying
> 1 MByte ROM takes about half an hour. The main suspect is nonexistent
> USB data buffering in the tester firmware.

There are a few tricks we could use to speed up SPI programming with
your hardware. flashrom already supports the Dediprog SF100 USB-based
SPI programmer, and that works well. Maybe we could use a similar
communication protocol, and/or use a serprog-like protocol directly on
top of libusb without the need of serial port emulation. The serial port
emulation is probably the biggest reason why anything is slow.

If you tell me about the design constraints of your device, I can
probably come up with a flashrom driver which can reflash an 1 MByte ROM
in ~5 minutes or so. That will require some cooperation from your
device, but should be doable with ~270 bytes of RAM. Even with ~140
bytes of RAM we should be able to get some decent performance. As long
as we can optimize the protocol, it should be possible to get acceptable
performance even with only 50 bytes of RAM, but generally more RAM will
give you better performance.

Side note: I think there once was a SPI-serprog design on the flashrom
mailing list, but I can't find it right now.

Regards,
Carl-Daniel

-- 
http://www.hailfinger.org/