linux-kernel - [PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

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Message-Id: <20210112052127.4557-1-yu.c.chen@intel.com>
Date:   Tue, 12 Jan 2021 13:21:27 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Len Brown <lenb@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chen Yu <yu.c.chen@...el.com>
Subject: [PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

Currently when turbo is disabled(either by BIOS or by the user), the
intel_pstate driver reads the max non-turbo frequency from the package-wide
MSR_PLATFORM_INFO(0xce) register. However on asymmetric platforms it is
possible in theory that small and big core with HWP enabled might have
different max non-turbo cpu frequency, because the MSR_HWP_CAPABILITIES
is percpu scope according to Intel Software Developer Manual.

The turbo max freq is already percpu basis in current code, thus make
similar change to the max non-turbo frequency as well.

Reported-by: Wendy Wang <wendy.wang@...el.com>
Signed-off-by: Chen Yu <yu.c.chen@...el.com>
---
v2: Per Srinivas' suggestion, avoid duplicated assignment of max_pstate.
v3: Per Rafael's suggestion, do not add new argument in intel_pstate_get_hwp_max()
    to avoid redundant local vars.
    Per Srinivas' suggestion, refined the commit log to reflect the 'non-turbo'
    max frequency.
--
 drivers/cpufreq/intel_pstate.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index eaf32ef7a030..99e180f644c3 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1724,11 +1724,9 @@ static void intel_pstate_max_within_limits(struct cpudata *cpu)
 static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
 {
 	cpu->pstate.min_pstate = pstate_funcs.get_min();
-	cpu->pstate.max_pstate = pstate_funcs.get_max();
 	cpu->pstate.max_pstate_physical = pstate_funcs.get_max_physical();
 	cpu->pstate.turbo_pstate = pstate_funcs.get_turbo();
 	cpu->pstate.scaling = pstate_funcs.get_scaling();
-	cpu->pstate.max_freq = cpu->pstate.max_pstate * cpu->pstate.scaling;
 
 	if (hwp_active && !hwp_mode_bdw) {
 		unsigned int phy_max, current_max;
@@ -1736,9 +1734,12 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
 		intel_pstate_get_hwp_max(cpu, &phy_max, &current_max);
 		cpu->pstate.turbo_freq = phy_max * cpu->pstate.scaling;
 		cpu->pstate.turbo_pstate = phy_max;
+		cpu->pstate.max_pstate = HWP_GUARANTEED_PERF(READ_ONCE(cpu->hwp_cap_cached));
 	} else {
 		cpu->pstate.turbo_freq = cpu->pstate.turbo_pstate * cpu->pstate.scaling;
+		cpu->pstate.max_pstate = pstate_funcs.get_max();
 	}
+	cpu->pstate.max_freq = cpu->pstate.max_pstate * cpu->pstate.scaling;
 
 	if (pstate_funcs.get_aperf_mperf_shift)
 		cpu->aperf_mperf_shift = pstate_funcs.get_aperf_mperf_shift();
-- 
2.17.1