On 19/06/18 11:25, Quentin Perret wrote: > On Tuesday 19 Jun 2018 at 12:19:01 (+0200), Juri Lelli wrote: > > 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 > > But there is not hard guarantee that the core_sibling mask and the > frequency domains are aligned :-( > > Hikey 620 is an example where they might be misaligned (I think)
Yep. In this case you'd need to write cpu_capacity twice (for each cluster). I think.
