On 19/06/18 11:02, Quentin Perret wrote: > On Tuesday 19 Jun 2018 at 11:47:14 (+0200), Juri Lelli wrote: > > On 19/06/18 10:40, Quentin Perret wrote: > > > Hi Pavan, > > > > > > On Tuesday 19 Jun 2018 at 14:48:41 (+0530), Pavan Kondeti wrote: > > > > [...] > > > > > > There seems to be a sysfs interface exposed by this driver to change > > > > cpu_scale. > > > > Should we worry about it? I don't know what is the usecase for changing > > > > the > > > > cpu_scale from user space. > > > > > > This is something I've been wondering as well. TBH, I'm not sure what to > > > do in this case. And I'm not sure to know what is the use-case either. > > > Debugging purpose I assume ? > > > > > > Juri, did you have a specific use-case for this feature when the > > > arch_topology driver was first introduced ? Or was it just to align > > > with the existing arm/arm64 code ? > > > > It was requested (IIRC) because DT might have bogus values and not be > > easily modifiable. So, this is another way to get things right for your > > platform at runtime. > > Right, but that also allows you to set different capacities to CPUs > inside the same freq domain, which isn't supported by the EM framework, > at least for now. So I would prefer to assume that your values in DT must > to be correct to use EAS, and leave the code as-is for now.
It's actually built on the (current) assumption that siblings share capacity [1], so it seems to align with what EM requires. [1] https://elixir.bootlin.com/linux/latest/source/drivers/base/arch_topology.c#L71
