Dne St 23. června 2010 21:00:19 Robert Jarzmik napsal(a):
> Marek Vasut <marek.va...@gmail.com> writes:
> > This patch does the following changes to cpufreq-pxa2xx:
> > 1) Simplifies the assembler code for frequency change
>
> OK, but did you think over what the old code was doing ?
> My guess is that all the jumps were there to trigger a load into the
> I-Cache before playing with memory timings. Did you consider that your new
> assembly fits fully into a cache line, and hence is protected from memory
> shutdown for the frequency change period ?
Good point, I'll rethink this. FTTB dropped from patchqueue.
>
> If you thought this over, then I would suggest to put a comment into the
> code to state that the assembly bit fits fully in one cache line. If not,
> I don't see clearly the benefit of removing the jumps ("b 2f" and "b 1b").
>
> And I didn't find the reference for the need of reading the MDREFR register
> after the write. Would you give me a pointer in the pxa27x TRM please ?
I believe the written data might be stuck in the Dcache, reading it back should
prevent this from happening. We certainly don't want to end with locked-up
machine, which I saw already. The reason is still unknown to me though.
Cheers
>
> Cheers.
>
> --
> Robert
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