On 30-07-20, 10:36, Lukasz Luba wrote: > On 7/30/20 10:10 AM, Sudeep Holla wrote: > > On Thu, Jul 30, 2020 at 02:23:33PM +0530, Viresh Kumar wrote: > > > On 29-07-20, 16:12, Lukasz Luba wrote: > > > > The existing CPUFreq framework does not tracks the statistics when the > > > > 'fast switch' is used or when firmware changes the frequency > > > > independently > > > > due to e.g. thermal reasons. However, the firmware might track the > > > > frequency > > > > changes and expose this to the kernel. > > > > > > > > This patch set aims to introduce CPUfreq statistics gathered by firmware > > > > and retrieved by CPUFreq driver. It would require a new API functions > > > > in the CPUFreq, which allows to poke drivers to get these stats. > > > > > > > > The needed CPUFreq infrastructure is in patch 1/4, patch 2/4 extends > > > > ARM SCMI protocol layer, patches 3/4, 4/4 modify ARM SCMI CPUFreq > > > > driver. > > > > > > Are you doing this for the fast switch case or because your platform > > > actually runs at frequencies which may be different from what cpufreq > > > core has requested ? > > > > > > > I think so. > > For both cases, but fast switch is major and present. Thermal is not > currently implemented in SCP FW, but might be in future.
Okay, lets simplify things a bit and merge things slowly upstream and merge only what is required right now. IIUC, the only concern right now is to capture stats with fast switch ? Maybe we can do something else in that case and brainstorm a bit.. > > > I am also not sure what these tables should represent, what the > > > cpufreq core has decided for the CPUs or the frequencies we actually > > > run at, as these two can be very different for example if the hardware > > > runs at frequencies which don't match exactly to what is there in the > > > freq table. I believe these are rather to show what cpufreq and its > > > governors are doing with the CPUs. > > > > > > > Exactly, I raised similar point in internal discussion and asked Lukasz > > to take up the same on the list. I assume it was always what cpufreq > > requested rather than what was delivered. So will we break the userspace > > ABI if we change that is the main question. > > Thank you for confirmation. If that is the mechanism for tracking what > cpufreq governors are doing with the CPUs, then is clashes with > presented data in FW memory, because firmware is the governor. Why is firmware the governor here ? Aren't you talking about the simple fast switch case only ? Over that, I think this cpufreq stats information isn't parsed by any tool right now and tweaking it a bit won't hurt anyone (like if we start capturing things a bit differently). So we may not want to worry about breaking userspace ABI here, if what we are looking to do is the right thing to do. > > > Over that I would like the userspace stats to work exactly as the way > > > they work right now, i.e. capture all transitions from one freq to > > > other, not just time-in-state. Also resetting of the stats from > > > userspace for example. All allocation and printing of the data must be > > > done from stats core, the only thing which the driver would do at the > > > end is updating the stats structure and nothing more. Instead of > > > reading all stats from the firmware, it will be much easier if you can > > > just get the information from the firmware whenever there is a > > > frequency switch and then we can update the stats the way it is done > > > right now. And that would be simple. > > > > > > > Good point, but notifications may not be lightweight. If that is no good, > > alternatively, I suggested to keep these firmware stats in a separate > > debugfs. Thoughts ? > > I agree that notifications might not be lightweight. I am not sure what notifications are we talking about here. > Furthermore I think > this still clashes with the assumption that cpufreq governor decisions > are tracked in these statistics, not the firmware decision. > > In this case I think we would have to create debugfs. > Sudeep do you think these debugfs should be exposed from the protocol > layer: > drivers/firmware/arm_scmi/perf.c > or maybe from the cpufreq scmi driver? I would probably be safer to have > it in the cpufreq driver because we have scmi_handle there. For the CPUs it would be better if we can keep things in cpufreq only, lets see how we go about it. -- viresh