[coreboot] [PATCH] flashrom: ST M25P40 bug?

[Carl-Daniel Hailfinger]

On 29.03.2008 22:58, Fredrik Tolf wrote:
> On Sat, 2008-03-29 at 22:17 +0100, Carl-Daniel Hailfinger wrote:
>   
>>> I'm attaching my patch to fix the problem. I would imagine that the
>>> other M25Pxx chips would be affected by the same problem, but since I
>>> can neither verify nor test what IDs they would have, they are excluded
>>> from my patch.
>>>       
>> Thanks for investigating and coding this. However, I have to veto the
>> patch in its current form. I know at least 4 flash chips with different
>> sizes from different manufacturers which have the same RES code.
>> Can you post the RDID output for your device? Maybe we can figure out a
>> way to identify it safely with the help of RDID and RES and possibly READ.
>>     
>
> The RDID output was just FF FF FF, so I'm pretty sure it just doesn't
> recognize the command at all.

Good. That means we can probably use RDID in combination with RES to
identify this special ST M25P40 variant.

> How do you suppose the chip's identity
> could be deduced from a READ command?
>   

You can read the contents of the chip and deduce a minimum size by
analyzing repetitions. While it is possible to underestimate the size of
the chip (in case 2^n identical images are behind each other), I can't
see a way to overestimate chip size.

> Would it perhaps not be wise to create a command-line switch to enable
> detection for chips like this, that might not be possible to
> auto-identify safely? The flashchip struct could be gifted with a
> pre-initialized boolean that indicates if a chip should be
> auto-identified without being explicitly specified.
>   

Yes, a command line switch would probably work, but I'm currently
working on a redesign of the SPI part of flashrom, so I'd like to delay
that a bit. Details will be announced after Tuesday.

Some parts of your patch (except the modification of the ST_M25P40
#define and the flashchips.c changes) are definitely worth merging
instantly, though. Could you split these parts from the patch and resend
them with a Signed-off-by statement?


Regards,
Carl-Daniel