On Wed, Dec 21, 2011 at 09:20:46AM +0800, Richard Zhao wrote: > On Tue, Dec 20, 2011 at 11:48:45PM +0000, Mark Brown wrote: > > Note also that not all hardware specifies things in terms of a fixed set > > of operating points, sometimes only the minimum voltage specification is > > varied with frequency or sometimes you see maximum and minimum stepping > > independently. > cpus that don't use freq table is out of scope of this driver. That's not the point - the point is that you may do something like specify a defined set of frequencies and just drop the minimum supported voltage without altering the maximum supported voltage as the frequency gets lower. > > Further note that if all hardware really does have as tight a set of > > requirements as you suggest then the regulator support in the driver > > needs to be non-optional otherwise a board without software regulator > > control might drop the frequency without also dropping the voltage. > It's ok to only adjuct freq without changes voltage. You can find many > arm soc cpufreq drivers don't change voltage. > If dts specify voltage but don't have such regulator. I'll assume it > always runs on the initial volatage (highest for most cases). My point exactly; such devices are examples of the policy outlined above where only the minimum voltage changes with frequency and the maximum voltage is constant. The cpufreq driver would lower the supported voltage when possible but wouldn't actually care if the voltage changes. > > > > - Frequencies that can't be supported due to limitations of the > > > > available supplies shouldn't be exposed to users. > > > As I said, only proved operation points are allowed. > > This statement appears to be unrelated to the comment you're replying > > to. > I meant the exact voltage can always successfull set. Anyway, I'll add This is just not the case. Regulators don't offer a continuous range of voltages, they offer steps of varying sizes which may miss setting some voltages, and board designers may choose not to support some of the voltage range. > regulator_set_voltage return value checking. While this is important the driver should also be enumerating the supported voltages at probe time and eliminating unsupportable settings so that governors aren't constantly trying to set things that can never be supported. The s3c64xx cpufreq driver provides an implementation of this. > Maybe I can remove it. But I'd probably add freq table dump. It's more important. > Agree? That seems like something the core should be doing if -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
