linux-kernel - [PATCH] cpufreq: intel_pstate: Drop redundant intel_pstate_get_hwp

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Date:   Fri, 10 Dec 2021 17:12:18 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PM <linux-pm@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: [PATCH] cpufreq: intel_pstate: Drop redundant intel_pstate_get_hwp_cap() call

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

It is not necessary to call intel_pstate_get_hwp_cap() from
intel_pstate_update_perf_limits(), because it gets called from
intel_pstate_verify_cpu_policy() which is either invoked directly
right before intel_pstate_update_perf_limits(), in
intel_cpufreq_verify_policy() in the passive mode, or called
from driver callbacks in a sequence that causes it to be followed
by an immediate intel_pstate_update_perf_limits().

Namely, in the active mode intel_cpufreq_verify_policy() is called
by intel_pstate_verify_policy() which is the ->verify() callback
routine of intel_pstate and gets called by the cpufreq core right
before intel_pstate_set_policy(), which is the driver's ->setoplicy()
callback routine, where intel_pstate_update_perf_limits() is called.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpufreq/intel_pstate.c |   18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -2486,18 +2486,14 @@ static void intel_pstate_update_perf_lim
 	 * HWP needs some special consideration, because HWP_REQUEST uses
 	 * abstract values to represent performance rather than pure ratios.
 	 */
-	if (hwp_active) {
-		intel_pstate_get_hwp_cap(cpu);
+	if (hwp_active && cpu->pstate.scaling != perf_ctl_scaling) {
+		int scaling = cpu->pstate.scaling;
+		int freq;

-		if (cpu->pstate.scaling != perf_ctl_scaling) {
-			int scaling = cpu->pstate.scaling;
-			int freq;
-
-			freq = max_policy_perf * perf_ctl_scaling;
-			max_policy_perf = DIV_ROUND_UP(freq, scaling);
-			freq = min_policy_perf * perf_ctl_scaling;
-			min_policy_perf = DIV_ROUND_UP(freq, scaling);
-		}
+		freq = max_policy_perf * perf_ctl_scaling;
+		max_policy_perf = DIV_ROUND_UP(freq, scaling);
+		freq = min_policy_perf * perf_ctl_scaling;
+		min_policy_perf = DIV_ROUND_UP(freq, scaling);
 	}

 	pr_debug("cpu:%d min_policy_perf:%d max_policy_perf:%d\n",