Re: [PATCH] b43: Fix MAC control and microcode init

[Michael Buesch <mb@bu3sch.de>]

On Thursday 24 January 2008 10:13:01 Johannes Berg wrote:
> 
> > This also adds a longer delay for waiting for the microcode
> > to initialize itself. It seems that the current timeout is sufficient
> > on all available devices, but there's no real reason why we shouldn't
> > wait for up to one second. Slow embedded devices might exist.
> 
> Your decision, but I very much doubt you can make the MAC any slower
> than on the old devices, in fact, on new chips it runs considerably
> faster I think.

Ok, well. But the host machine does get faster. In theory we only
gave the microcode 500 microseconds of time to initialize. I think
that is is a pretty tiny timeframe. In practice the time was higher,
because we had a loop that checked MMIO and delayed for 10usec.
Of course this all has overhead. But as machines get faster and faster
I think we can't assume to have more than 500 microseconds of time.

So, increasing the delay to one second doesn't hurt anyone. In
all common cases it will continue after a few milliseconds. That's fine.
Even if there is something going wrong (wrong firmware) you can
interrupt the one second delay by hitting ^C.

I think the specs originally sayed to use a much longer delay than
we were using. But we did use a shorter delay, because in some old
bcm43xx code this ran unter spinlock as far as I remember. So we didn't
want to spin several milliseconds and lockup the system, if something
goes wrong in firmware. These times are gone and now we can sleep
in this part of the code.

-- 
Greetings Michael.