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 > externally. > > Becoming obsoleted by more advanced, less intrusive hardware debugging > methods. > > - 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 > voice. > I have used this option a lot, it has been very useful in hardware (CPU) debugging. > > Ralf -- _ _ ____ ___ Carsten Langgaard Mailto:carstenl@mips.com |\ /|||___)(___ MIPS Denmark Direct: +45 4486 5527 | \/ ||| ____) Lautrupvang 4B Switch: +45 4486 5555 TECHNOLOGIES 2750 Ballerup Fax...: +45 4486 5556 Denmark http://www.mips.com
