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Wysocki" Date: Fri, 10 Sep 2021 17:45:38 +0200 Message-ID: Subject: Re: [PATCH] cpufreq: intel_pstate: Override parameters if HWP forced by BIOS To: Doug Smythies Cc: "Rafael J. Wysocki" , Srinivas Pandruvada , Len Brown , Linux Kernel Mailing List , Linux PM Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 10, 2021 at 5:35 PM Doug Smythies wrote: > > On Fri, Sep 10, 2021 at 4:18 AM Rafael J. Wysocki wrote: > > On Fri, Sep 10, 2021 at 5:14 AM Doug Smythies wrote: > > > On Thu, Sep 9, 2021 at 10:22 AM Rafael J. Wysocki wrote: > > > > On Thu, Sep 9, 2021 at 6:12 PM Rafael J. Wysocki wrote: > > > > > On Thu, Sep 9, 2021 at 3:20 PM Doug Smythies wrote: > > > > > > On Thu, Sep 9, 2021 at 4:18 AM Rafael J. Wysocki wrote: > > > > > > > On Thu, Sep 9, 2021 at 8:52 AM Srinivas Pandruvada > > > > > > > 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 > > > > > > > > > --- > > > > > > > > > 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. OK > I currently have limited access to a computer that doesn't force > HWP via BIOS.