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 00:59:02 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Alexander Monakov <amonakov@...ras.ru>
Cc:     Huang Rui <ray.huang@....com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Alex Deucher <alexander.deucher@....com>,
        Jason Bagavatsingham <jason.bagavatsingham@...il.com>,
        "Pierre-Loup A . Griffais" <pgriffais@...vesoftware.com>,
        Nathan Fontenot <nathan.fontenot@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Borislav Petkov <bp@...e.de>, x86@...nel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v4] x86, sched: Fix the AMD CPPC maximum perf on some
 specific generations


* 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 ...

Thanks,

	Ingo