linux-kernel - [PATCH] cpufreq: CPPC: Add u64 casts to avoid overflowing

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Message-Id: <20221220101225.3190672-1-pierre.gondois@arm.com>
Date:   Tue, 20 Dec 2022 11:12:25 +0100
From:   Pierre Gondois <pierre.gondois@....com>
To:     linux-kernel@...r.kernel.org
Cc:     james.clark@....com, Ionela.Voinescu@....com,
        Pierre Gondois <pierre.gondois@....com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-pm@...r.kernel.org
Subject: [PATCH] cpufreq: CPPC: Add u64 casts to avoid overflowing

The fields of the _CPC object are unsigned 32-bits values.
To avoid overflows while using _CPC's values, add 'u64' casts.

Signed-off-by: Pierre Gondois <pierre.gondois@....com>
---
 drivers/cpufreq/cppc_cpufreq.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 432dfb4e8027..022e3555407c 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -487,7 +487,8 @@ static unsigned int get_perf_level_count(struct cpufreq_policy *policy)
 	cpu_data = policy->driver_data;
 	perf_caps = &cpu_data->perf_caps;
 	max_cap = arch_scale_cpu_capacity(cpu);
-	min_cap = div_u64(max_cap * perf_caps->lowest_perf, perf_caps->highest_perf);
+	min_cap = div_u64((u64)max_cap * perf_caps->lowest_perf,
+			  perf_caps->highest_perf);
 	if ((min_cap == 0) || (max_cap < min_cap))
 		return 0;
 	return 1 + max_cap / CPPC_EM_CAP_STEP - min_cap / CPPC_EM_CAP_STEP;
@@ -519,10 +520,10 @@ static int cppc_get_cpu_power(struct device *cpu_dev,
 	cpu_data = policy->driver_data;
 	perf_caps = &cpu_data->perf_caps;
 	max_cap = arch_scale_cpu_capacity(cpu_dev->id);
-	min_cap = div_u64(max_cap * perf_caps->lowest_perf,
-			perf_caps->highest_perf);
-
-	perf_step = CPPC_EM_CAP_STEP * perf_caps->highest_perf / max_cap;
+	min_cap = div_u64((u64)max_cap * perf_caps->lowest_perf,
+			  perf_caps->highest_perf);
+	perf_step = div_u64((u64)CPPC_EM_CAP_STEP * perf_caps->highest_perf,
+			    max_cap);
 	min_step = min_cap / CPPC_EM_CAP_STEP;
 	max_step = max_cap / CPPC_EM_CAP_STEP;
 
-- 
2.25.1