Ralf Baechle wrote:
> On Fri, Nov 29, 2002 at 12:56:10PM +0100, Maciej W. Rozycki wrote:
> > > We've talked about this before - the specification of the ll/sc
> > > instructions says they only work ok on cached memory. In the real world
> > > they seem to work also in uncached memory but I'd not bet the farm on
> > > that, too many implementations out there, too many chances for subtle
> > > bugs.
> > Indeed -- CONFIG_MIPS_UNCACHED should either be removed or imply
> > CONFIG_CPU_HAS_LLSC=n. I suppose there is some interest in the option, so
> > the latter is preferable. That would imply moving the option into the CPU
> > configuration section as now it's set very late, long after
> > CONFIG_CPU_HAS_LLSC is set. Or it could be set up the other way, i.e. the
> > option would only become available if CONFIG_CPU_HAS_LLSC had been set to
> > n. There would be no need to move it then.
> > What do you think?
> I had the same thought. So far there are the following groups of people
> using this option:
> - Hardware people using it so the the entire program is becoming visible
> Becoming obsoleted by more advanced, less intrusive hardware debugging
> - Software people kluding around bugs in their software.
> Don't expect me to support this. Note with a line of code.
> - For testing if the cache code is actually working.
> Will only be useful to show big fat bugs. For the more subtle bugs
> there is no way at all around understanding the entire cache managment
> thing including all subtilities. Actually a good reason to not support
> this option either.
> It's been my observation that hardly any user is aware of these consquences
> nor is the Linux code making a good attempt at complying with all the
> additional restrictions of running uncached. So in my oppinion
> CONFIG_MIPS_UNCACHED should go. But I don't feel very strong about it so
> I'm going to wait for a few days so others have a chance to raise their
I have used this option a lot, it has been very useful in hardware (CPU)
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