On Mon, Mar 4, 2019 at 7:06 PM Srinivas Pandruvada <srinivas.pandruv...@linux.intel.com> wrote: > > [...] > > > There are other methods like PL1 budget limit for such cases. FW > > > can > > > just change the config TDP level. > > > > OK, but that would be done without notification I suppose? > > There is a notification via processor PCI device (B0D4). This is passed > to user space to change the power limits. The new element is called > PPCC and it is exposed via sysfs.
What do you mean by "new element" and how exactly is it exposed? > Disabling turbo is not very interesting as there can be more turbo than > non turbo. So you loose lots of performance. So instead you can control > power in turbo region to give you more control. _PPC is even less > interesting as you can't control uncore power. I guess that designers should know about that. The kernel is on the receiving end here. :-) > > > > > > That's fair enough, but the point is that the driver doesn'dev_t > > > > do > > > > the right thing even if the platform does send a _PPC > > > > notification. > > > > > > _PPC notification is to indicate levels in _PSS not to > > > disable/enable > > > turbo via IA32_MISC_*. > > > > I was not talking about notifications, but about what the driver does > > when MSR_IA32_MISC_ENABLE_TURBO_DISABLE is set or unset by FW on the > > fly: this only really works if the change is from unset to set, > > because the range of frequencies to use is restricted then, even > > though user-visible policy limits are not updated. However, if the > > change is from set to unset, the update of policy limits is actually > > necessary for the change to really take effect (otherwise the user > > policy max prevents turbo frequencies from being requested). HWP > > seems to be affected too, for that matter, because the upper limit in > > the MSR is not updated too then AFAICS. > > > > > The platform could have just set _PPC to 1 or to TAR-1. Here _PPC > > > is sent for somthing more than just changing _PSS max > > > level. Do we have bug in if _PPC just changes performance level? > > > > I think that we just need to live with the fact that _PPC may be > > triggered for something more than changing _PSS max. > > I understand the reason why you are doing the change. I investigated > this bugzilla before. I was thinking can udev rules should be enough to > address this issue. But it was not a requirement. > > The change itself is fine. Except may be hide the policy->rwsem in some > header file instead of directly exposing to clients to use. I'm not sure what you mean. I guess that you are talking about intel_pstate_update_max_freq() which acquires policy->rwsem. If so, what exactly is the problem with it?
