On 02/25/2014 10:11 AM, Viresh Kumar wrote: > On 18 February 2014 07:49, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote: >> On 18 February 2014 03:30, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: >>> On Monday, February 17, 2014 02:25:34 PM Srivatsa S. Bhat wrote: >>>> Why go to no_policy when we can actually set things right? >>>> >>>> Anyway, I am not arguing against this strongly. I just wanted to share my >>>> thoughts, since this is the approach that made more sense to me. >>> >>> And I agree with that. In particular, since we're going to set the new >>> policy *anyway* at this point, we can adjust the current frequency just fine >>> in the process, can't we? >> >> Though I still feel that it wouldn't be the right thing to do as get() >> just can't >> return zero. Actually I was planning to place a WARN() over its return value >> of zero. A WARN() would definitely be good. >> >> Anyway, as two of the three are in favor of this we can get that in.. But how >> would that work? >> >> - What frequency should we call cpufreq_driver_target ? >> - Remember that it wouldn't do anything if policy->cur is same as new freq. >> - Also remember that drivers need special attention if new freq is > old >> freq or vice versa. As they will change voltage before or after change here. >> And because we actually don't know what frequency we are at currently, how >> will we decide that? > Hmm, that's a good point. However, lets first think about the simple scenario that the driver _is_ able to detect the current frequency from the hardware (a non-zero, sane value) say X KHz, and that frequency is different from what the cpufreq subsystem thinks it is (Y KHz). In the current code, when we observe this, we send out a notification and try to adjust to X KHz. Instead, what I'm suggesting is to invoke the driver to set the frequency to Y KHz, since that's what the cpufreq subsystems wants the frequency to be at. As for the case where the driver reports the frequency to be 0 KHz, we can print a WARN() and try to force set the frequency to Y KHz. But if that turns out to be too tricky to handle, we can just put a WARN() and error out, as you proposed earlier. Regards, Srivatsa S. Bhat -- 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
