Linus Walleij wrote: > I've felt a need for clock notifiers and we've cheated by using > CPUfreq because it so happens that the clocking in system-wide > and whenever the CPU freq change so may the other clocks. > > But if I put code into a PrimeCell MMC/SPI/I2C driver or whatever and > use CPUfreq that's very unelegant, and for other platforms where > the CPU freq don't change when this particular device clk freq > change plain misleading. > > A clk pre/postchange notifier pair would really help and would > make for elegant drivers that can handle clock freq transitions. > A lot of ARM chips have peripherals that are driven by PLLs that run quasi-independently of the CPU clock. If I guess correctly at what is being described above, a notifier chain for the users of a clock would be a clean way for peripherals to deal with clock speed *and* CPU speed changes, indeed. A clock source that was affected by cpufreq would place itself on the cpufreq notifier chain, and also provide a notifier chain for peripherals that are driven by that clock. When a cpufreq notification arrived, if the clock couldn't adjust for the cpufreq change it would use its notifier chain to tell all downstream peripherals about it. A lot of peripherals could then focus just on the clock notifier chain, and would no longer care about cpufreq. I like it. b.g. -- Bill Gatliff bgat@xxxxxxxxxxxxxxx _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
