linux-kernel - Re: [PATCH v4] x86, sched: Fix the AMD CPPC maximum perf on some specific generations

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Date:   Thu, 13 May 2021 18:27:46 +0800
From:   Huang Rui <ray.huang@....com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Alexander Monakov <amonakov@...ras.ru>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        Jason Bagavatsingham <jason.bagavatsingham@...il.com>,
        "Pierre-Loup A . Griffais" <pgriffais@...vesoftware.com>,
        "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Borislav Petkov <bp@...e.de>,
        "x86@...nel.org" <x86@...nel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v4] x86, sched: Fix the AMD CPPC maximum perf on some
 specific generations

On Thu, May 13, 2021 at 06:12:14PM +0800, Ingo Molnar wrote:
> 
> * Huang Rui <ray.huang@....com> wrote:
> 
> > On Thu, May 13, 2021 at 06:59:02AM +0800, Ingo Molnar wrote:
> > > 
> > > * Alexander Monakov <amonakov@...ras.ru> wrote:
> > > 
> > > > On Sun, 25 Apr 2021, Huang Rui wrote:
> > > > 
> > > > > Some AMD Ryzen generations has different calculation method on maximum
> > > > > perf. 255 is not for all asics, some specific generations should use 166
> > > > > as the maximum perf. Otherwise, it will report incorrect frequency value
> > > > > like below:
> > > > 
> > > > The commit message says '255', but the code:
> > > > 
> > > > > --- a/arch/x86/kernel/cpu/amd.c
> > > > > +++ b/arch/x86/kernel/cpu/amd.c
> > > > > @@ -1170,3 +1170,19 @@ void set_dr_addr_mask(unsigned long mask, int dr)
> > > > >  		break;
> > > > >  	}
> > > > >  }
> > > > > +
> > > > > +u32 amd_get_highest_perf(void)
> > > > > +{
> > > > > +	struct cpuinfo_x86 *c = &boot_cpu_data;
> > > > > +
> > > > > +	if (c->x86 == 0x17 && ((c->x86_model >= 0x30 && c->x86_model < 0x40) ||
> > > > > +			       (c->x86_model >= 0x70 && c->x86_model < 0x80)))
> > > > > +	    return 166;
> > > > > +
> > > > > +	if (c->x86 == 0x19 && ((c->x86_model >= 0x20 && c->x86_model < 0x30) ||
> > > > > +			       (c->x86_model >= 0x40 && c->x86_model < 0x70)))
> > > > > +	    return 166;
> > > > > +
> > > > > +	return 225;
> > > > > +}
> > > > 
> > > > says 225? This is probably a typo? In any case they are out of sync.
> > > > 
> > > > Alexander
> > > 
> > > Ugh - that's indeed a good question ...
> > > 
> > 
> > Ah sorry! It's my typo. It should be 255 (confirmed in the ucode).
> > 
> > Alexander, thanks a lot to catch this!
> > 
> > Ingo, would you mind to update it from 225 -> 255 while you apply this
> > patch or let me know if you want me to send v5?
> 
> No need to send v5, done!
> 
> I have a system that appears to be affected by this bug:
> 
>   kepler:~> lscpu | grep -i mhz
>   CPU MHz:                         4000.000
>   CPU max MHz:                     7140.6250
>   CPU min MHz:                     2200.0000
> 
> So I should be able to confirm after a reboot.
> 

Thanks! Please feel free to let me know whether it's able to fix your
machine. :-)

Thanks,
Ray