[coreboot] SST25VF016B (2MB) flash on m57sli (IT8716F).

Ronald Hoogenboom ronald at zonnet.nl
Sun Jan 20 12:48:46 CET 2008

On Sun, 2008-01-20 at 11:59 +0100, Ronald Hoogenboom wrote:
> The read status register will take at least:
> 16*(2/33) us = about 1 us (excluding the LPC latency, which is....?), so 
> assuming that the first read status will show busy and the second will 
> show ready, it is only 2 us slower: ~20%, so that should be acceptable. 
> I'll do some checks on the hardware shortly.
I've done the tests and the programming result (eg. the data read back
from the flash) is correct with and without the status reading.
With status reading, programming takes:
1'15 ~ 1'50
Without status reading, programming takes:
0'50 ~ 0'55

There is quite some variance in the time taken extra by reading the
status, the lower bound is about the expected penalty (as calculated
above), but the higher bound is not so easily explainable without better
understanding. If you think this performance hit is acceptable, then go
for it, put the status reading back in, I would say.

Maybe it would be nice to have some kind of progress bar, like in 'rpm
-Uhv', 'scp' or 'cdparanoia', at least while programming the flash,
especially when the programming times get over a few minutes, as can be
expected with these bigger and bigger serial flash devices.

Maybe there should also be support for partial erasing and programming
(depending on what the device allows).


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