linux-kernel - Re: [PATCH 01/14] cpufreq/amd-pstate: Show a warning when a CPU fails to setup

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Message-ID: <Z6oELkyt+XEMp/nk@BLRRASHENOY1.amd.com>
Date: Mon, 10 Feb 2025 19:20:38 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
Cc: Mario Limonciello <superm1@...nel.org>, Perry Yuan <perry.yuan@....com>,
	"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <linux-kernel@...r.kernel.org>,
	"open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>,
	Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH 01/14] cpufreq/amd-pstate: Show a warning when a CPU
 fails to setup

On Mon, Feb 10, 2025 at 05:29:24PM +0530, Dhananjay Ugwekar wrote:
> On 2/7/2025 3:26 AM, Mario Limonciello wrote:
> > From: Mario Limonciello <mario.limonciello@....com>
> > 
> > I came across a system that MSR_AMD_CPPC_CAP1 for some CPUs isn't
> > populated.  This is an unexpected behavior that is most likely a
> > BIOS bug. In the event it happens I'd like users to report bugs
> > to properly root cause and get this fixed.
> 
> I'm okay with this patch, but I see a similar pr_debug in caller cpufreq_online(),
> so not sure if this is strictly necessary.
> 
> 1402                 /*
> 1403                  * Call driver. From then on the cpufreq must be able
> 1404                  * to accept all calls to ->verify and ->setpolicy for this CPU.
> 1405                  */
> 1406                 ret = cpufreq_driver->init(policy);
> 1407                 if (ret) {
> 1408                         pr_debug("%s: %d: initialization failed\n", __func__,
> 1409                                  __LINE__);
> 1410                         goto out_free_policy;
> 1411                  
>

Well, the pr_debug() doesn't always get printed unless the loglevel is
set to debug, which is usually done by the developers and not the end
users.

However you have a point that since the code jumps to free_cpudata1 on
failures from amd_pstate_init_perf(), amd_pstate_init_freq(),
amd_pstate_init_boost_support(), freq_qos_add_request(). So the
pr_warn() doesn't indicate that the failure is due to
MSR_AMD_CPPC_CAP1 not being populated.

-- 
Thanks and Regards
gautham.



> Thanks,
> Dhananjay
> 
> > 
> > Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> > ---
> >  drivers/cpufreq/amd-pstate.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> > index f425fb7ec77d7..573643654e8d6 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -1034,6 +1034,7 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
> >  free_cpudata2:
> >  	freq_qos_remove_request(&cpudata->req[0]);
> >  free_cpudata1:
> > +	pr_warn("Failed to initialize CPU %d: %d\n", policy->cpu, ret);
> >  	kfree(cpudata);
> >  	return ret;
> >  }
> > @@ -1527,6 +1528,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> >  	return 0;
> >  
> >  free_cpudata1:
> > +	pr_warn("Failed to initialize CPU %d: %d\n", policy->cpu, ret);
> >  	kfree(cpudata);
> >  	return ret;
> >  }
>