linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Add additional OOB enabling bit

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Message-ID: <89e856e6c76b460c1515b70677e44bc50033bc17.camel@linux.intel.com>
Date:   Fri, 12 Jun 2020 08:45:54 -0700
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     Doug Smythies <dsmythies@...us.net>, lenb@...nel.org,
        viresh.kumar@...aro.org, rjw@...ysocki.net
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: intel_pstate: Add additional OOB enabling bit

On Fri, 2020-06-12 at 07:11 -0700, Doug Smythies wrote:
> On 2020.06.11 10:49 Srinivas Pandruvada wrote:
> 
> > Add additional bit for OOB (Out of band) enabling of P-states. In
> > this
> > case intel_pstate shouldn't load. Currently, only "BIT(8) == 1" of
> > the
> > MSR MSR_MISC_PWR_MGMT is considered as OOB. Also add "BIT(18) == 1"
> > as
> > OOB condition.
> 
> Shouldn't those bits be defined in these files:
> arch/x86/include/asm/msr-index.h
> and
> tools/arch/x86/include/asm/msr-index.h
> 
> ?
The rule from arch-x86 maintainers requires use in more than one place
to go there.

> 
> By the way, I couldn't find those bits defined in Intel docs that I
> have.
Usually, they end up in data sheets.

>  
> > Signed-off-by: Srinivas Pandruvada <
> > srinivas.pandruvada@...ux.intel.com>
> > ---
> >  drivers/cpufreq/intel_pstate.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cpufreq/intel_pstate.c
> > b/drivers/cpufreq/intel_pstate.c
> > index 8e23a698ce04..f21761443c90 100644
> > --- a/drivers/cpufreq/intel_pstate.c
> > +++ b/drivers/cpufreq/intel_pstate.c
> > @@ -2686,8 +2686,8 @@ static bool __init
> > intel_pstate_platform_pwr_mgmt_exists(void)
> >  	id = x86_match_cpu(intel_pstate_cpu_oob_ids);
> >  	if (id) {
> >  		rdmsrl(MSR_MISC_PWR_MGMT, misc_pwr);
> > -		if (misc_pwr & (1 << 8)) {
> > -			pr_debug("Bit 8 in the MISC_PWR_MGMT MSR
> > set\n");
> > +		if ((misc_pwr & BIT(8)) || (misc_pwr & BIT(18))) {
> 
> And then those bit definitions used above.
I didn't understand the comment.

> 
> > +			pr_debug("Bit 8 or 18 in the MISC_PWR_MGMT MSR
> > set\n");
> 
> And then some insight also printed  with the debug message.
> At least say "Out of Band".
We can.

Thanks,
Srinivas

> 
> >  			return true;
> >  		}
> >  	}
> > --
> > 2.24.1
> 
>