linux-kernel - Re: [PATCH] x86/cpu: Update power flags

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Date:   Tue, 28 Nov 2023 20:25:40 +0100
From:   Thomas Weißschuh <linux@...ssschuh.net>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/cpu: Update power flags

On 2023-11-28 20:12:17+0100, Borislav Petkov wrote:
> On Tue, Nov 28, 2023 at 07:54:54PM +0100, Thomas Weißschuh wrote:
> > As described on page 99 of
> > "Processing Programming Reference (PPR) for AMD Family 19h Model 61h, Revision B1 Processor".
> > (AMD Documentation Hub Document 56713)
> > 
> > Tested on an "AMD Ryzen 7 7840U w/ Radeon  780M Graphics".
> > 
> > Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> > ---
> >  arch/x86/kernel/cpu/powerflags.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/arch/x86/kernel/cpu/powerflags.c b/arch/x86/kernel/cpu/powerflags.c
> > index fd6ec2aa0303..0c98405aeae2 100644
> > --- a/arch/x86/kernel/cpu/powerflags.c
> > +++ b/arch/x86/kernel/cpu/powerflags.c
> > @@ -21,4 +21,7 @@ const char *const x86_power_flags[32] = {
> >  	"eff_freq_ro", /* Readonly aperf/mperf */
> >  	"proc_feedback", /* processor feedback interface */
> >  	"acc_power", /* accumulated power mechanism */
> > +	"connected_standby", /* connected standby */
> > +	"rapl", /* running average power limit */
> > +	"fast_cppc", /* fast collaborative processor performance control */
> 
> No need.
> 
> The beginning of Documentation/arch/x86/cpuinfo.rst tries to explain
> why.

Isn't this introduction more about the cpuinfo "flags" fields?
These power management flags have their own field "power management".

Without the patch it looks like this on my machine in cpuinfo:

  power management: ts ttp tm hwpstate cpb eff_freq_ro [13] [14] [15]

So they are already reported, but only their numeric value.

Anyways, if it's not correct to have them then let's drop the patch.


Thomas