linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Fix HWP on boot CPU after system resume

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Message-ID: <20160502021212.GE2855@vireshk-i7>
Date:	Mon, 2 May 2016 07:42:12 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: intel_pstate: Fix HWP on boot CPU after system
 resume

On 02-05-16, 02:27, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Commit 41cfd64cf49fc "Update frequencies of policy->cpus only from
> ->set_policy()" changed the way the intel_pstate driver's ->set_policy
> callback updates the HWP (hardware-managed P-states) settings.
> A side effect of it is that if those settings are modified on the
> boot CPU during system suspend and wakeup, they will never be
> restored during subsequent system resume.
> 
> To address this problem, allow cpufreq drivers that don't provide
> ->target or ->target_index callbacks to use ->suspend and ->resume
> callbacks and add a ->resume callback to intel_pstate to restore
> the HWP settings on the CPUs that belong to the given policy.
> 
> Fixes: 41cfd64cf49fc "Update frequencies of policy->cpus only from ->set_policy()"
> Tested-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> Note: We've tried to address that issue by adding syscore_ops to
> intel_pstate and restoring the boot CPU's HWP setting from a
> syscore resume, but that turns out to be too early (apparently,
> the processor is not ready for that at that point).
> 
> ---
>  drivers/cpufreq/cpufreq.c      |   28 ++++++++++++++++------------
>  drivers/cpufreq/intel_pstate.c |   12 ++++++++++--
>  2 files changed, 26 insertions(+), 14 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh