[flashrom] [PATCH] ft2232_spi.c: add frequency divider parameter.

Stefan Tauner stefan.tauner at student.tuwien.ac.at
Sat Mar 31 00:05:19 CEST 2012


On Sat, 31 Mar 2012 00:52:14 +0900
Samir Ibradžić <sibradzic at gmail.com> wrote:

> On 2012年03月07日 00:25, Stefan Tauner wrote:
> > On Tue, 28 Feb 2012 11:50:37 +0900
> > Samir Ibradžić<sibradzic at gmail.com>  wrote:

> >> But i vote for supporting specific divider after all, one can never know
> >> if there is some obscure device out there in the wild that supports only
> >> 6365372Hz.
> >
> > well we could support both actually... selecting the divider as in our
> > patch, or alternatively the frequency (if it is not possible print the
> > next lower available one)...
> >
> > anyway this can be done later and i'd like to get this into svn
> > now-ish rather than wait for the perfect patch. you do not happen to
> > own a logic analyzer that could confirm that the frequency now is
> > really what we think it is, do you?
> 
> Sorry, no analyzer available here. I can confirm though, that when using 
> bigger dividers, data transfer speeds achieved matches the calculated 
> frequencies, at least on the device i have here (PicoTAP).

by "matches" you mean that e.g. doubling the divisor approximately
doubles the time needed for an read/erase/write, right?

> > in any case could you please test the patch i have sent so that we know
> > it does not break the programmer completely?
> 
> Already tested, seems ok. Anyway, we just need to be careful that the 
> patch has zero consequences when "spispeed" option is not used at all.

thanks for testing.
yes (though i think you meant divisor not spispeed?), altough zero
consequences need to be specified more precisely:
the previous code set divisor 2 by sending 0 to the device. our new
code does the same by setting DEFAULT_DIVISOR to 2 and doing the math
right. so from the programmers point of view the communication should
be equal.

> >
> > if you like to work on a followup patch please use "spispeed" as the
> > parameter for the frequency because that is the one used in serprog and
> > the buspirate already.
> >
> 
> Do you have any updates, or i can re-base on top of your previous patch?

no updates yet, but i will change this bit because it does seem like a
typo:
 	 * Hence the expressible divisors are all even numbers between 2 and
-	 * 2^17 (=131072) resulting in SCK frequencies of 2 MHz down to about
+	 * 2^17 (=131072) resulting in SCK frequencies of 6 MHz down to about
 	 * 92 Hz for 12 MHz inputs.
 	 */

it would be nice if someone could really verify the correct
frequencies on the output pins, but if no one will do that in the next
days/weeks, i will commit it anyway.
-- 
Kind regards/Mit freundlichen Grüßen, Stefan Tauner




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