linux-kernel - Re: [PATCH 1/2][v2] cpufreq: intel_pstate: Add parameter to get guarantee frequency

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Message-ID: <CAJZ5v0i5F3kFOxzAax1RS9etrLtzLBuPRoqvbQM=NwuonFZDVw@mail.gmail.com>
Date:   Mon, 11 Jan 2021 13:44:09 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Wendy Wang <wendy.wang@...el.com>
Subject: Re: [PATCH 1/2][v2] cpufreq: intel_pstate: Add parameter to get
 guarantee frequency

On Mon, Jan 11, 2021 at 8:40 AM Chen Yu <yu.c.chen@...el.com> wrote:
>
> Add input parameter to receive guarantee pstate from intel_pstate_get_hwp_max()
> for later use.

I'm not a fan of this change, because the new argument will only be
needed in one place where intel_pstate_get_hwp_max() and it requires
adding redundant local vars and pointless updates elsewhere.

Besides, in intel_pstate_get_cpu_pstates() you can do something like
this after calling intel_pstate_get_hwp_max():

cpu->pstate.max_pstate = HWP_GUARANTEED_PERF(READ_ONCE(cpu->hwp_cap_cached));
cpu->pstate.max_freq = cpu->pstate.max_pstate * cpu->pstate.scaling;