On Thu, Mar 20, 2008 at 07:59:41PM -0400, Jerry Van Baren wrote: > Per Andy (and my limited reading of the UMs), some 83xx have the PMR > registers and some don't. The compiler either supports the PMR register > or it doesn't. If you make it runtime configurable, people running CPUs > that don't support the specific PMR will have to change compiler > configurations in order to compile with the PMR register in there (could > have unintended consequences).
I'm not saying make it runtime-only -- you can still have a config option to determine whether to build a kernel that supports it. I'm saying there should be an additional runtime check so that if you run a multiplatform kernel with perfmon enabled on a chip that doesn't support it, you won't take a program check. > Also, if you look at the code (arch/powerpc/kernel/pmc.c), there are > several different types of PMR registers, based on the core and flavor > of the core. Finding or making a compiler setup that supports all of > the possible PMR registers could be a problem. It only needs to support all possible registers within a class of hardware over which we support multiplatform kernels. > You would still have to make the PMR read/write runtime selectable > because the CPUs that don't support that register will raise an > exception IIRC (an Really Bad Thing[tm]). Yes, that was my point. The changelog on the patch seemed to indicate that the compile-time option was intended to address this, not just the toolchain problem. -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
