Date: Mon, 08 Mar 2010 13:49:57 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: ticso@cicely.de, ticso@cicely7.cicely.de Cc: arm@freebsd.org Subject: Re: RM9200 tuning Message-ID: <20100308.134957.431102609571835335.imp@bsdimp.com> In-Reply-To: <20100308202337.GF11192@cicely7.cicely.de> References: <20100308202337.GF11192@cicely7.cicely.de>
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In message: <20100308202337.GF11192@cicely7.cicely.de>
Bernd Walter <ticso@cicely7.cicely.de> writes:
: Originally FreeBSD had assumed fixed clock rates.
Only for the first few revs. Now it is settable with the
AT91_MASTER_CLOCK option.
: Knowing the peripheral rate is important for e.g. UART bps dividers.
: I think in the meantime it is possible to reconfigure the kernel to
: different clock rates - if yes what are the kernel options for it?
: Which would be the best place to reconfigure the PLL?
: I know how to do it and that it is done by the loader right now, but
: I would like to have it as a kernel tuneable.
: All I need to know is a good place in the kernel startup.
Hmmm, I thought the kernel tried to read the master clock rate, but I
can't find the code that does it anymore. The AT91 family have a
register than can be read to get this value, so long as your board
design conforms to the atmel documented restrictions on the clock xtal
used.
Or, as is usually the case with clocks on these parts, am I confusing
this with something else :)
Warner
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