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[31.26.103.238]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-49d26bf9490sm10925625e9.9.2026.09.09.12.24.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2026 12:24:07 -0700 (PDT) From: Oleg Keri To: Catalin Marinas , Will Deacon , Mark Rutland , Sumit Gupta , Beata Michalska , Prasanna Kumar T S M , 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 Subject: [PATCH v2 1/2] arm64: topology: fix arch_freq_get_on_cpu() overflow above 4.19 GHz Date: Wed, 9 Sep 2026 21:23:50 +0200 Message-ID: <20260909192351.33910-2-okerixx@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909192351.33910-1-okerixx@gmail.com> References: <20260909192351.33910-1-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") Suggested-by: Jonathan Cameron 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DE0C0C79FB9 for ; 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[31.26.103.238]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-49d26bf9490sm10925625e9.9.2026.09.09.12.24.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2026 12:24:07 -0700 (PDT) From: Oleg Keri To: Catalin Marinas , Will Deacon , Mark Rutland , Sumit Gupta , Beata Michalska , Prasanna Kumar T S M , 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 Subject: [PATCH v2 1/2] arm64: topology: fix arch_freq_get_on_cpu() overflow above 4.19 GHz Date: Wed, 9 Sep 2026 21:23:50 +0200 Message-ID: <20260909192351.33910-2-okerixx@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909192351.33910-1-okerixx@gmail.com> References: <20260909192351.33910-1-okerixx@gmail.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260909_122412_130241_49EFA0D6 X-CRM114-Status: GOOD ( 12.67 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org 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") Suggested-by: Jonathan Cameron 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 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv