Re: [PATCH] cpufreq: acpi_cpufreq: base frequency attribute support

From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>
Subject: Re: [PATCH] cpufreq: acpi_cpufreq: base frequency attribute support
Date: Thu, 25 Feb 2016 10:07:52 -0800	[thread overview]
Message-ID: <1456423672.17628.9.camel@linux.intel.com> (raw)
In-Reply-To: <20160225032700.GA2822@vireshk-i7>

On Thu, 2016-02-25 at 08:57 +0530, Viresh Kumar wrote:
> On 24-02-16, 15:37, Srinivas Pandruvada wrote:
> > Good I tested again.
> > 
> > Hi Viresh,
> > 
> > Are we no longer allowed to call
> > 	sysfs_create_file in cpufreq_driver.init() callback?
> > 
> > The following call crashes because of BUG_ON for !kobj->sd:
> > 	sysfs_create_file(&policy->kobj,
> >                                  
> > &(cpufreq_attr_base_frequency.attr));
> > 
> > Before I debug further, I want to check with you.
> > This used to work before.
> 
> Haven't checked that yet, but you should be using cpufreq_driver.attr
> for this
> kind of stuff, isn't it ?
If I use cpufreq_driver.attr, then it will create sysfs attribute for
every system using acpi-cpufreq, whether they can support it or not.
This change is only needed for the later generation of Intel CPUs
(IvyBridge and later). 
There is no standard ACPI way to know the base frequency if we add
attribute for all systems using acpi-cpufreq.

Thanks,
Srinivas

>