Messages in this thread | | | Date | Mon, 18 Dec 2017 14:08:20 +0530 | From | Gautham R Shenoy <> | Subject | Re: [v3 PATCH 2/3] powernv-cpufreq: Fix pstate_to_idx() to handle non-continguous pstates |
| |
Hi Balbir,
On Sun, Dec 17, 2017 at 02:15:25PM +1100, Balbir Singh wrote: > On Wed, Dec 13, 2017 at 5:57 PM, Gautham R. Shenoy > <ego@linux.vnet.ibm.com> wrote: > > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> > > > > The code in powernv-cpufreq, makes the following two assumptions which > > are not guaranteed by the device-tree bindings: > > > > 1) Pstate ids are continguous: This is used in pstate_to_idx() to > > obtain the reverse map from a pstate to it's corresponding > > entry into the cpufreq frequency table. > > > > 2) Every Pstate should always lie between the max and the min > > pstates that are explicitly reported in the device tree: This > > is used to determine whether a pstate reported by the PMSR is > > out of bounds. > > > > Both these assumptions are unwarranted and can change on future > > platforms. > > While this is a good thing, I wonder if it is worth the complexity. Pstates > are contiguous because they define transitions in incremental value > of change in frequency and I can't see how this can be broken in the > future?
In the future, we can have the OPAL firmware give us a smaller set of pstates instead of expose every one of them. As it stands today, for most of the workloads, we will need at best 20-30 pstates and not beyond that.
> > Balbir Singh. >
-- Thanks and Regards gautham.
| |