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From: Oleg Keri <okerixx@gmail.com>
To: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Beata Michalska <beata.michalska@arm.com>,
	Sumit Gupta <sumitg@nvidia.com>,
	Prasanna Kumar T S M <ptsm@linux.microsoft.com>,
	Russell King <linux@armlinux.org.uk>,
	Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>,
	Sudeep Holla <sudeep.holla@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Danilo Krummrich <dakr@kernel.org>,
	Viresh Kumar <viresh.kumar@linaro.org>
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
Subject: Re: [PATCH v1 1/2] arm64: topology: fix arch_freq_get_on_cpu() overflow above 4.19 GHz
Date: Wed,  9 Sep 2026 21:18:16 +0200	[thread overview]
Message-ID: <178898149654.33757.7826789084252321894@gmail.com> (raw)
In-Reply-To: <20260909113625.000063be@oss.qualcomm.com>

Good point - that reads much better than reusing scale as scratch.  Taken
for v2:

	scale = arch_scale_freq_capacity(cpu);
	freq = (scale * arch_scale_freq_ref(cpu)) >> SCHED_CAPACITY_SHIFT;

Same semantics, and it makes it obvious that both the multiply and the
shift stay in 64 bits and only the final value is narrowed - which is the
whole point of the fix.

Agreed on leaving arch_scale_freq_capacity() out of the expression too.
This file is arm64 only, so unsigned long is 64 bits and it would be safe
here, but it stops being self-evident to the reader and the cast that
would make it evident is worse than keeping the temporary.

Thanks for the review.

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

WARNING: multiple messages have this Message-ID (diff)
From: Oleg Keri <okerixx@gmail.com>
To: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Beata Michalska <beata.michalska@arm.com>,
	Sumit Gupta <sumitg@nvidia.com>,
	Prasanna Kumar T S M <ptsm@linux.microsoft.com>,
	Russell King <linux@armlinux.org.uk>,
	Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>,
	Sudeep Holla <sudeep.holla@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Danilo Krummrich <dakr@kernel.org>,
	Viresh Kumar <viresh.kumar@linaro.org>
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
Subject: Re: [PATCH v1 1/2] arm64: topology: fix arch_freq_get_on_cpu() overflow above 4.19 GHz
Date: Wed,  9 Sep 2026 21:18:16 +0200	[thread overview]
Message-ID: <178898149654.33757.7826789084252321894@gmail.com> (raw)
In-Reply-To: <20260909113625.000063be@oss.qualcomm.com>

Good point - that reads much better than reusing scale as scratch.  Taken
for v2:

	scale = arch_scale_freq_capacity(cpu);
	freq = (scale * arch_scale_freq_ref(cpu)) >> SCHED_CAPACITY_SHIFT;

Same semantics, and it makes it obvious that both the multiply and the
shift stay in 64 bits and only the final value is narrowed - which is the
whole point of the fix.

Agreed on leaving arch_scale_freq_capacity() out of the expression too.
This file is arm64 only, so unsigned long is 64 bits and it would be safe
here, but it stops being self-evident to the reader and the cast that
would make it evident is worse than keeping the temporary.

Thanks for the review.

  reply	other threads:[~2026-09-09 19:18 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-06 16:37 [PATCH v1 0/2] arm64/cpufreq: report and track frequencies above 4.19 GHz Oleg Keri
2026-09-06 16:37 ` Oleg Keri
2026-09-06 16:37 ` [PATCH v1 1/2] arm64: topology: fix arch_freq_get_on_cpu() overflow " Oleg Keri
2026-09-06 16:37   ` Oleg Keri
2026-09-09 18:36   ` Jonathan Cameron
2026-09-09 18:36     ` Jonathan Cameron
2026-09-09 19:18     ` Oleg Keri [this message]
2026-09-09 19:18       ` Oleg Keri
2026-09-06 16:37 ` [PATCH v1 2/2] cpufreq: update capacity_freq_ref when the boost state changes Oleg Keri
2026-09-06 16:37   ` Oleg Keri

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