[coreboot] Probe missing on W49F002U

[Peter Stuge]

On Mon, Mar 03, 2008 at 09:36:33AM +0800, Jun Ma wrote:
> > There is almost certainly an additional write control line on
> > this board, and you will have to find it.
> >
> > It's not too hard to do, let us know if you would like to try.
> 
> I have a PCCHIP SIS530 board right in my hand, and datasheets for
> SIS530/SIS5595/W49F002U.

Great! This is helpful.


> but I haven't got any SCH or PCB files for this board,  maybe I
> should read the W49F002U DS first?

Yes, that is a good start. Then probably the southbridge (5595?) to
find out about GPIO pins.


> when you talked about "an additional write control line on this
> board", do you mean it was not the problem caused by the BIOS chip?

Correct. Board vendors frequently connect a GPIO signal to the flash
chip write protect input, in order to protect the flash chip from
unintended writes.


> All SIS530/SIS5595 boards have the same problem?

Each board vendor can use different GPIO signals, and some may choose
to not use any GPIO but disable write protect by connecting it
directly to logic 0 or 1, so that there is no "protection."


> Would 'amiflash at Win32' or other flash routings have the same
> problem?

amiflash knows how to control this write protection, other flash
routines may or may not. uniflash for example can call flash
operations in the existing BIOS which know how to control the
protection.


> PS: the original BIOS chip for this board is ASD AE29F2008-12, It
> also can't be readed by flashrom(and the model was not listed in
> flashrom README file).

Ok, if it is not very different from the other supported flash chips
it should not be very difficult to add.


> Can you guide me in a better direction? I will try my best on this
> test.

In order to find out about the GPIO you can either:
* Use a multimeter to check if any GPIO pin on the southbridge is
  connected to the flash chip write protect
* Save all GPIO registers from booting with factory BIOS
  Compare with GPIO registers from booting with coreboot
  Set one GPIO register bit at a time and test if flashrom can
  identify the flash chip automatically. (That requires write to work
  correctly.)


Best regards

//Peter