On Wed, 4 Sep 2002, Dominic Sweetman wrote:
> Well, next time, get your board designers to think before they map...
>
> It's generally better to map some DRAM low (for boot ROMs and other
> stupid programs you don't want to make big-address aware), then remap
> the whole DRAM to some very high address for Linux. Much better than
> forcing you to use the TLB (or XKPHYS, if you've a 64-bit CPU) to get
> at I/O.
Hmm, what's the deal? Other processors always use MMU to access iomem...
> Bear in mind that there *isn't a 64-bit mode*. Privileged code (which
> is everything except Linux applications) can always run 64-bit
> instructions; all addresses are 64-bits really, it's just the
> sign-extension of the registers which makes you think you've got
> 32-bit pointers. Usually a 64-bit CPU can access XKPHYS any time
> it can access I/O registers.
Well, it's mostly a programming convention. Without going into details,
arch/mips is the 32-bit mode and arch/mips64 is the 64-bit one. The usual
approximation is the state of cp0.kx, even though 64-bit operations do
indeed work when ~cp0.kx.
--
+ Maciej W. Rozycki, Technical University of Gdansk, Poland +
+--------------------------------------------------------------+
+ e-mail: macro@ds2.pg.gda.pl, PGP key available +
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