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[31.26.103.238]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-49e2212193esm2595255e9.1.2026.09.09.23.34.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2026 23:34:58 -0700 (PDT) From: Oleg Keri To: Catalin Marinas , Will Deacon , Mark Rutland , Sumit Gupta , Prasanna Kumar T S M , Beata Michalska , Russell King , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Sudeep Holla , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Viresh Kumar Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, driver-core@lists.linux.dev, linux-pm@vger.kernel.org, jonathan.cameron@oss.qualcomm.com, sibi.sankar@oss.qualcomm.com Subject: [PATCH v3 1/2] arm64: topology: fix arch_freq_get_on_cpu() overflow above 4.19 GHz Date: Thu, 10 Sep 2026 08:34:39 +0200 Message-ID: <20260910063440.4677-2-okerixx@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260910063440.4677-1-okerixx@gmail.com> References: <20260910063440.4677-1-okerixx@gmail.com> Precedence: bulk X-Mailing-List: driver-core@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit arch_freq_get_on_cpu() computes the product of the frequency scale and the reference frequency as a u64, but assigns it to an unsigned int before shifting it back down: freq = scale * arch_scale_freq_ref(cpu); freq >>= SCHED_CAPACITY_SHIFT; The product is truncated to 32 bits before the shift, so the result wraps once arch_scale_freq_ref() exceeds 2^32 / SCHED_CAPACITY_SCALE, i.e. 4194304 kHz. On a Snapdragon X2 Elite (Glymur) laptop, whose boost OPP is 4723200 kHz, cpuinfo_avg_freq reports 524283 kHz instead of ~4723200 kHz while the CPU demonstrably runs at the boost frequency: a fixed workload completes in 1.72 s at the 4723200 kHz OPP versus 2.01 s at 4032000 kHz, matching the 1.171 frequency ratio. Keep the arithmetic in 64 bits until after the shift. Fixes: 16d1e27475f6 ("arm64: Provide an AMU-based version of arch_freq_get_on_cpu") Signed-off-by: Oleg Keri --- arch/arm64/kernel/topology.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c index d28438f8b83f..0eca321ff113 100644 --- a/arch/arm64/kernel/topology.c +++ b/arch/arm64/kernel/topology.c @@ -245,8 +245,7 @@ int arch_freq_get_on_cpu(int cpu) * (see amu_scale_freq_tick for details) */ scale = arch_scale_freq_capacity(cpu); - freq = scale * arch_scale_freq_ref(cpu); - freq >>= SCHED_CAPACITY_SHIFT; + freq = (scale * arch_scale_freq_ref(cpu)) >> SCHED_CAPACITY_SHIFT; return freq; } -- 2.55.0