From: Greg KH <gregkh@linuxfoundation.org>
To: z00314508 <zhengzucheng@huawei.com>
Cc: rafael@kernel.org, viresh.kumar@linaro.org, tglx@linutronix.de,
len.brown@intel.com, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency
Date: Fri, 11 Mar 2022 09:33:12 +0100 [thread overview]
Message-ID: <YisJSKZ5RvswarnW@kroah.com> (raw)
In-Reply-To: <20220311081111.159639-1-zhengzucheng@huawei.com>
On Fri, Mar 11, 2022 at 04:11:11PM +0800, z00314508 wrote:
> From: Zucheng Zheng <zhengzucheng@huawei.com>
>
> On some specific platforms, the cpufreq driver does not define
> cpufreq_driver.get() routine (eg:x86 intel_pstate driver), as a
> result, the cpufreq_get() can't get the correct CPU frequency.
>
> Modern x86 processors include the hardware needed to accurately
> calculate frequency over an interval -- APERF, MPERF and the TSC.
> Here we use arch_freq_get_on_cpu() in preference to any driver
> driver-specific cpufreq_driver.get() routine to get CPU frequency.
>
> Fixes: f8475cef9008 ("x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF")
> Signed-off-by: Zucheng Zheng <zhengzucheng@huawei.com>
> ---
> drivers/cpufreq/cpufreq.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 80f535cc8a75..d777257b4454 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1806,10 +1806,14 @@ unsigned int cpufreq_get(unsigned int cpu)
> {
> struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> unsigned int ret_freq = 0;
> + unsigned int freq;
>
> if (policy) {
> down_read(&policy->rwsem);
> - if (cpufreq_driver->get)
> + freq = arch_freq_get_on_cpu(policy->cpu);
> + if (freq)
> + ret_freq = freq;
> + else if (cpufreq_driver->get)
> ret_freq = __cpufreq_get(policy);
> up_read(&policy->rwsem);
>
> --
> 2.18.0.huawei.25
>
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
next prev parent reply other threads:[~2022-03-11 8:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-11 8:11 [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency z00314508
2022-03-11 8:33 ` Greg KH [this message]
2022-03-11 15:52 ` Rafael J. Wysocki
2022-03-15 2:30 ` zhengzucheng
2022-03-15 10:47 ` Rafael J. Wysocki
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