linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Simplify intel_pstate_update_perf

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Date:   Fri, 9 Apr 2021 20:01:57 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH] cpufreq: intel_pstate: Simplify
 intel_pstate_update_perf_limits()

On Wed, Apr 07, 2021 at 04:21:55PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Because pstate.max_freq is always equal to the product of
> pstate.max_pstate and pstate.scaling and, analogously,
> pstate.turbo_freq is always equal to the product of
> pstate.turbo_pstate and pstate.scaling, the result of the
> max_policy_perf computation in intel_pstate_update_perf_limits() is
> always equal to the quotient of policy_max and pstate.scaling,
> regardless of whether or not turbo is disabled.  Analogously, the
> result of min_policy_perf in intel_pstate_update_perf_limits() is
> always equal to the quotient of policy_min and pstate.scaling.
> 
> Accordingly, intel_pstate_update_perf_limits() need not check
> whether or not turbo is enabled at all and in order to compute
> max_policy_perf and min_policy_perf it can always divide policy_max
> and policy_min, respectively, by pstate.scaling.  Make it do so.
> 
> While at it, move the definition and initialization of the
> turbo_max local variable to the code branch using it.
> 
> No intentional functional impact.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Tested-by: Chen Yu <yu.c.chen@...el.com>