On Tue, Sep 12, 2006 at 10:33:28AM +0200, Pavel Machek wrote: > Hi! > > > > > >No, there is reason to keep that in kernel -- so that cpufreq > > > > >userspace interface can be kept, and so that resulting kernel<->user > > > > >interface is not ugly. > > > > Cpuferq defines cpufreq_frequency_table structure in arch independent > > > > header while it's arch dependent data structure. A lot of code is built > > > > around this invalid basic brick and therefore is invalid: cpufreq tables, > > > > interface with cpu freq drivers, etc. Notion of transition latency as it > > > > defined by cpufreq is wrong because it's not a function of cpu type but > > > > function of current and next operating point. no runtime control on > > > > operating points set. it's always the same set of operating points for all > > > > system cpus in smp case and no way to define different sets or track any > > > > dependencies in case say multi core cpus. insufficient kernel<->user space > > > > interface to handle embedded requirements and no way to extend it within > > > > current design. Shall I continue? Why should then anyone want to keep > > > > cpufreq userspace interface just due to keep it? > > > > > > Yes, please continue. I do not think we can just rip cpufreq interface > > > out of kernel, and I do not think it is as broken as you claim it > > > is. Ripping interface out of kernel takes years. > > > > > > I'm sure cpufreq_frequency_table could be moved to asm/ header if you > > > felt strongly about that. > > > > > > I believe we need to fix cpufreq if it is broken for embedded > > > cases. > > > > cpufreq is broken at the cpufreq_driver interface for embedded > > applications needing control over more than one control variable at a > > time. > > > > That interface only supports setting target frequencies, and expanding it > > to set target frequencies and voltages is not possible without something > > like PowerOP. Adding the types of parameters to cpufreq would likely > > make cpufreq a mess. > > Can we at least try adding that, before deciding cpufreq is unsuitable > and starting new interface? I do not think issues are nearly as big as > you think.. (at user<->kernel interface level, anyway; you'll need big > changes under the hood). We are trying. The PowerOP patches from Matt and Eugeny start to put into place some of the kernel mode plumbing for this in a way that avoids thrashing the existing models, and it addresses the needs of the operating point PM community. Which is large in the CE and Embedded camps. --mgross
