Montreal Linux Power Management Mini-Summit, July 13, 2009 - Meeting Notes

Linus Walleij at
Tue Sep 1 18:22:14 EDT 2009

2009/7/31 Len Brown <lenb at>:

> A Linux Power Management "mini-summit" was held on July 13th, 2009 -
> on the first day of the Montreal Linux Symposium.
> (...)

> SH running cpufreq on top of clock framework
>        cpufreq has notifiers, clock framework does not

Hm! Paul can you elaborate on what that was about.

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.

Has anyone poked at this?

Linus Walleij

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