On 12/07/17 05:09, Viresh Kumar wrote: > On 11-07-17, 16:06, Dietmar Eggemann wrote: >> But in the meantime we're convinced that cpufreq_driver_fast_switch() is >> not the right place to call arch_set_freq_scale() since for (future) >> arm/arm64 fast-switch driver, the return value of >> cpufreq_driver->fast_switch() does not give us the information that the >> frequency value did actually change. > > Yeah, I saw your discussion with Peter on #linux-rt IRC and TBH I wasn't aware > that we are going to do fast switching that way. Just trying to get > understanding of that idea a bit.. > > So we will do fast switching from scheduler's point of view, i.e. we wouldn't > schedule a kthread to change the frequency. But the real hardware still can't > do > that without sleeping, like if we have I2C somewhere in between. AFAIU, we > will > still have some kind of *software* bottom half to do that work, isn't it? And > it > wouldn't be that we have pushed some instructions to the hardware, which it > can > do a bit later. >
No the platforms we are considering are only where a standard firmware interface is provided and the firmware deals with all those I2C/PMIC crap. > For example, the regulator may be accessed via I2C and we need to program that > before changing the clock. So, it will be done by some software code only. > Software but just not Linux OSPM but some firmware(remote processors presumably, can't imagine on the same processor though) -- Regards, Sudeep
