[flashrom] SST 49LF0008A - Erase problem (and solution)

[Sean Nelson]

On 3/8/10 5:41 AM, Panino ColSalame wrote:
>
> Hello,
>
> I'm playing with flashrom on an ASEM Industrial PC based on an Atom Z530 and the US15W (Poulsbo) System Controller Hub.
> The BIOS flash is the SST 49LF0008A (Firmware Hub).
>
> After downloading the latest development code using git, flashrom was able to detect and read the flash, but the erase command failed.
>
> At first I've tried to increase the delay that is used by the toggle functions in jedec.c, passing from the default 8 to 80 (just for testing).
> At this point, the Erase command started to work properly.
>
>    
The proper solution would to use the longer delay; in your case. It is 
possible there's a problem/bug with your system.
> SST manual reads:
> The End-of-Write detection mode is incorporated into the FWH Read cycle.
> The actual completion of the nonvolatile write is asynchronous with the system; therefore, either a Data# Polling or Toggle Bit read
> may be simultaneous with the completion of the Write cycle.
> If this occurs, the system may possibly get an erroneous result, i.e., valid data may appear to conflict with either DQ7 or DQ6.
> In order to prevent spurious rejection, if an erroneous result occurs, the software routine should include a loop to read the accessed location an additional two (2) times.
> If both reads are valid, then the device has completed the Write cycle, otherwise the rejection is valid.
>
>
> So, I've set the delay for reading the toggle bit again to the default value of 8 and I've added an additional toggle bit check, in case the first one seems to be ok.
>
>    
The toggle check does a continuous read until it gets the correct data, 
you just changed the loop so it would work for you but is not a fix. It 
adds extraneous reads in a while loop.
> It works!
>
> So, I'm able to Read, Write and Erase the chip.
>
>
> Best Regards
>
> Panino
>    
Nacked because of the previously mentioned points.