Messages in this thread | | | From | Balbir Singh <> | Date | Wed, 3 Jan 2018 23:47:58 +1100 | Subject | Re: [v3 PATCH 2/3] powernv-cpufreq: Fix pstate_to_idx() to handle non-continguous pstates |
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On Wed, Jan 3, 2018 at 11:07 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > On Monday, December 18, 2017 9:38:20 AM CET Gautham R Shenoy wrote: >> 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. > > I'm not sure about the status here. > > Is this good to go as is or is it going to be updated? >
I have no major objections, except some of the added complexity, but Gautham makes a point that this is refactoring for the future
Balbir Singh.
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