Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210909034802.1708-1-dsmythies@telus.net> <223a72d91cfda9b13230e4f8cd6a29f853535277.camel@linux.intel.com>
 <CAJZ5v0gn8rpTiVqkXgGqPFDH8-BKTYGiypM-2A2q1jJLm6HbCQ@mail.gmail.com>
 <CAAYoRsWdFwiwo8j2Nc-vhk2mnoZqJC9fyS7URtEz3E1VxfNbLQ@mail.gmail.com>
 <CAJZ5v0hO7SajJ5HFVDcma6nOfzy-289MdwUSiJbY8Hm3mxvXnQ@mail.gmail.com>
 <CAJZ5v0j1JjLr0co06yJCCNV2p06e91Zh7tkMXoGTE=waB5Xo1Q@mail.gmail.com>
 <CAAYoRsUun0_tXTEGi6m1L0A9ffRWZ8FbLs1kFEZ0d0QQi+ssQw@mail.gmail.com> <CAJZ5v0jMDbxXt_EWN-GUOGBDCpDGHUoqRoTtfR8-rUOQjDBUyw@mail.gmail.com>
In-Reply-To: <CAJZ5v0jMDbxXt_EWN-GUOGBDCpDGHUoqRoTtfR8-rUOQjDBUyw@mail.gmail.com>
From:   Doug Smythies <dsmythies@telus.net>
Date:   Fri, 10 Sep 2021 08:34:59 -0700
Message-ID: <CAAYoRsVOh+TxZK8BWfM=u6YqEhSY-Pgpt+aavZGBLogVTEocKw@mail.gmail.com>
Subject: Re: [PATCH] cpufreq: intel_pstate: Override parameters if HWP forced
 by BIOS
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Len Brown <len.brown@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        dsmythies <dsmythies@telus.net>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Sep 10, 2021 at 4:18 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
> On Fri, Sep 10, 2021 at 5:14 AM Doug Smythies <dsmythies@telus.net> wrote:
> > On Thu, Sep 9, 2021 at 10:22 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > > On Thu, Sep 9, 2021 at 6:12 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > > > On Thu, Sep 9, 2021 at 3:20 PM Doug Smythies <dsmythies@telus.net> wrote:
> > > > > On Thu, Sep 9, 2021 at 4:18 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > > > > > On Thu, Sep 9, 2021 at 8:52 AM Srinivas Pandruvada
> > > > > > <srinivas.pandruvada@linux.intel.com> wrote:
> > > > > > >
> > > > > > > On Wed, 2021-09-08 at 20:48 -0700, Doug Smythies wrote:
> > > > > > > > If HWP has been already been enabled by BIOS, it may be
> > > > > > > > necessary to override some kernel command line parameters.
> > > > > > > > Once it has been enabled it requires a reset to be disabled.
> > > > > > > >
> > > > > > > > Signed-off-by: Doug Smythies <dsmythies@telus.net>
> > > > > > > > ---
> > > > > > > >  drivers/cpufreq/intel_pstate.c | 22 ++++++++++++++++------
> > > > > > > >  1 file changed, 16 insertions(+), 6 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/cpufreq/intel_pstate.c
> > > > > > > > b/drivers/cpufreq/intel_pstate.c
> > > > > > > > index bb4549959b11..073bae5d4498 100644
> > > > > > > > --- a/drivers/cpufreq/intel_pstate.c
> > > > > > > > +++ b/drivers/cpufreq/intel_pstate.c
> > > > > > > > @@ -3267,7 +3267,7 @@ static int __init intel_pstate_init(void)
> > > > > > > >                  */
> > > > > > > >                 if ((!no_hwp && boot_cpu_has(X86_FEATURE_HWP_EPP)) ||
> > > > > > > >                     intel_pstate_hwp_is_enabled()) {
> > > > > > > > -                       hwp_active++;
> > > > > > > > +                       hwp_active = 1;
> > > > > > > Why this change?
> > > > > >
> > > > > > I think hwp_active can be changed to bool and then it would make sense
> > > > > > to update this line.
> > > > > >
> > > > > > > >                         hwp_mode_bdw = id->driver_data;
> > > > > > > >                         intel_pstate.attr = hwp_cpufreq_attrs;
> > > > > > > >                         intel_cpufreq.attr = hwp_cpufreq_attrs;
> > > > > > > > @@ -3347,17 +3347,27 @@ device_initcall(intel_pstate_init);
> > > > > > > >
> > > > > > > >  static int __init intel_pstate_setup(char *str)
> > > > > > > >  {
> > > > > > > > +       /*
> > > > > > > > +        * If BIOS is forcing HWP, then parameter
> > > > > > > > +        * overrides might be needed. Only print
> > > > > > > > +        * the message once, and regardless of
> > > > > > > > +        * any overrides.
> > > > > > > > +        */
> > > > > > > > +       if(!hwp_active
> > > > > > > This part of code is from early_param, Is it possible that
> > > > > > > hwp_active is not 0?
> > > > > >
> > > > > > Well, it wouldn't matter even if it were nonzero.  This check is just
> > > > > > pointless anyway.
> > > > > >
> > > > > > > > && boot_cpu_has(X86_FEATURE_HWP))
> > > > > > > > +               if(intel_pstate_hwp_is_enabled()){
> > > > > >
> > > > > > This should be
> > > > > >
> > > > > > if (boot_cpu_has(X86_FEATURE_HWP) && intel_pstate_hwp_is_enabled()) {
> > > > >
> > > > > Disagree.
> > > > > This routine gets executed once per intel_pstate related grub command
> > > > > line entry. The purpose of the "if(!hwp_active" part is to prevent the
> > > > > printing of the message to the logs multiple times.
> > > >
> > > > Ah OK.  Fair enough.
> > > >
> > > > You can do all of the checks in one conditional, though.  They will be
> > > > processed left-to-right anyway.
> > > >
> > > > But then it would be good to avoid calling
> > > > intel_pstate_hwp_is_enabled() multiple times if it returns false.
> > > >
> > > > And having said all that I'm not sure why you are trying to make
> > > > no_hwp depend on !hwp_active?  I will not be taken into account anyway
> > > > if intel_pstate_hwp_is_enabled() returns 'true'?
> > > >
> > > > So if no_hwp is covered regardless, you may move the
> > > > intel_pstate_hwp_is_enabled() inside the no_load conditional.
> > > >
> > > > Alternatively, and I would do that, intel_pstate_hwp_is_enabled()
> > > > could be evaluated earlier in intel_pstate_init() and if it returned
> > > > 'true', both no_load and no_hwp would be disregarded.
> > >
> > > Something like the attached, for the record.
> >
> > O.K. and Thanks.
> > I was trying to avoid this line getting into the log:
> >
> > [    0.000000] intel_pstate: HWP disabled
> >
> > only to overridden later by, now, these lines:
> >
> > [    0.373742] intel_pstate: HWP enabled by BIOS
> > [    0.374177] intel_pstate: Intel P-state driver initializing
> > [    0.375097] intel_pstate: HWP enabled
> >
> > Let me see if I can go with your suggestion and get to
> > what I had hoped to get in the logs.
>
> It would be sufficient to put the "disabled" printk() after the
> "no_hwp" if () statement in intel_pstate_init().  See attached.

Agreed, thanks. Yes, I was thinking similar.

> BTW, I've changed the message to "HWP not enabled", because that's
> what really happens to be precise.

Agreed. Good idea.

Give me a fews days to create and test a formal patch.
I currently have limited access to a computer that doesn't force
HWP via BIOS.

... Doug