Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH] cpufreq: powernv: Define methods to parse positive & negative pstates | Date | Wed, 06 Dec 2017 23:41:32 +1100 |
| |
Gautham R Shenoy <ego@linux.vnet.ibm.com> writes:
> Hi Michael, > > On Wed, Dec 06, 2017 at 09:54:27PM +1100, Michael Ellerman wrote: >> Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> writes: >> >> > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> >> > >> > Pstates are 8bit values but on POWER8 they are negative and on POWER9 >> > they are positive. This patch adds helper routines to differentiate >> > the sign to read the correct pstate value. >> >> This sounds like it could be a bad bug, but I can't really tell from the >> change log. What is the actual impact of not having this patch? > > On some POWER9 platforms, there can be more than 128 pstates. > > Without this patch, on such platforms, if the value of the current > frequency corresponds to a pstate greater than 128, then the code will > interpret it as a negative number, and report that the "pstate is out > of bound" while returning a nominal frequency.
OK, that's good detail to have in the change log, please include it.
>> Should it have a Fixes/Cc-stable tag? > > This doesn't fix any prior commit, but is fixes a newly discovered > bug.
OK. You could say it "fixes" the commit that added Power9 support to the driver, but it seems there wasn't really a commit that did that specifically.
> I will resend the patch Cc'ing stable.
You don't have to Cc stable, that was just a suggestion. Though it sounds like the symptoms are probably bad enough to warrant it.
cheers
| |