Hi, While grepping for CPU_FREQ in the kernel sources I found some CPU frequency scaling code in arch/mips/au1000/common/power.c As a common cross-architecture CPU frequency scaling infrastructure exists in 2.6. kernels, and it offers a few interesting tidbits: - support for dynamic frequency scaling if the hardware allows for it (low latencies caused by switching, and many switchings in a second are possible) - handling of loops_per_jiffy updates, i.e. no need to do a lengthy calibrate_delay() - unified user interface, i.e. developers/users switching from ARM to MIPS will find the CPU frequency interface at the same place in sysfs - informs "notifiers" of frequency switches. While the baud rate update in au1000/common/power.c seems to be a good candidate for such a notifier, it might be necessary to update the baud rate so fast that it needs to be done inside the are locked by pm_lock, and without a few function calls' overhead in between. Or isn't this a problem? Therefore, I'd suggest that we update arch/mips/au1000/common/power.c to use the cpufreq infrastructure. It is located at drivers/cpufreq/, besides cpufreq.c one or more governors (currently [2.6.9-rc2] four exist, powersave, performance, userspace and ondemand) are needed. Keeping the old ctl_table interface around as a wrapper for the cpufreq interfaces looks to be possible[*]; I'd like to #ifdef CONFIG_... and deprecate it, though. As I don't have MIPS hardware [well, I do, inside a WRT54G router, but that's besides the point], don't have and don't want to have a cross-compiling infrastructure here, I can neither compile-test nor real-life-test any patches I submit. Nonetheless I'd be willing to write a "suggestion" on how to update arch/mips/au1000/common/power.c, and somebody with compiler and hardware could test it then. Are there other MIPS CPUs which support CPU frequency scaling? If so, it'd be great if the maintainers for these specific platforms are aware of the CPUfreq infrastructure, evaluate whether it's good enough for their needs, and possibly add cpufreq drivers for these CPUs. For any questions, comments or patches regarding the cpufreq core or cpufreq drivers, there's a mailing list at cpufreq AT www DOT linux DOT org DOT uk, which is also CC'ed on this message. Maintainer of cpufreq is Dave Jones. Thanks for listening, Dominik [*] we already keep a few such old interfaces around, but they'll be removed soon after 2005 begins. They'll not become available on MIPS in the meantime, of course.
