linux-kernel - [PATCH v2] cpufreq: Limit resolving a frequency to policy min/max

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Date: Tue, 27 Feb 2024 14:43:51 +0530
From: Shivnandan Kumar <quic_kshivnan@...cinc.com>
To: <rafael@...nel.org>, Viresh Kumar <viresh.kumar@...aro.org>,
        "Vincent
 Donnefort" <vincent.donnefort@....com>
CC: <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_pkondeti@...cinc.com>, <quic_namajain@...cinc.com>,
        <quic_rgottimu@...cinc.com>, kernel <kernel@...cinc.com>,
        Shivnandan Kumar
	<quic_kshivnan@...cinc.com>,
        <stable@...r.kernel.org>
Subject: [PATCH v2] cpufreq: Limit resolving a frequency to policy min/max

Resolving a frequency to an efficient one should not transgress policy->max
(which can be set for thermal reason) and policy->min. Currently there is
possibility where scaling_cur_freq can exceed scaling_max_freq when
scaling_max_freq is inefficient frequency. Add additional check to ensure
that resolving a frequency will respect policy->min/max.

Cc: <stable@...r.kernel.org>
Fixes: 1f39fa0dccff ("cpufreq: Introducing CPUFREQ_RELATION_E")
Signed-off-by: Shivnandan Kumar <quic_kshivnan@...cinc.com>
--

Changes in v2:
-rename function name from cpufreq_table_index_is_in_limits to cpufreq_is_in_limits
-remove redundant outer parenthesis in return statement
-Make comment single line

--
---
 include/linux/cpufreq.h | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index afda5f24d3dd..7741244dee6e 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -1021,6 +1021,19 @@ static inline int cpufreq_table_find_index_c(struct cpufreq_policy *policy,
 						   efficiencies);
 }
 
+static inline bool cpufreq_is_in_limits(struct cpufreq_policy *policy,
+						    int idx)
+{
+	unsigned int freq;
+
+	if (idx < 0)
+		return false;
+
+	freq = policy->freq_table[idx].frequency;
+
+	return freq == clamp_val(freq, policy->min, policy->max);
+}
+
 static inline int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
 						 unsigned int target_freq,
 						 unsigned int relation)
@@ -1054,7 +1067,8 @@ static inline int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
 		return 0;
 	}
 
-	if (idx < 0 && efficiencies) {
+	/* Limit frequency index to honor policy->min/max */
+	if (!cpufreq_is_in_limits(policy, idx) && efficiencies) {
 		efficiencies = false;
 		goto retry;
 	}
-- 
2.25.1