From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4F927171D1 for ; Tue, 7 Nov 2023 10:38:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="P8DR9XQV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D2C9C433C7; Tue, 7 Nov 2023 10:38:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699353497; bh=vJRAI9RGy/58A+FlzWE10PI0MfMhXjXb/jXWE3sfgoA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=P8DR9XQVqGWE/jSsPbBMbBE96MY+i3o2DaeBsP5f6BDjvx/DOhiZNZZkcqIWdiFKJ TQMPoAXJ0x2TtXE67Y62VjspTbRGAOufa4CRGNzTRwseWqPxAx2JnJvge/Pd8SFd/C 652UC6kbexqs2g1LA//blK+R2I/ceR0tGVIZOvphJyLJCKGKy/GV+1hSXjmqkt/xhR QmDw9YouENrjpbSlFvRNGZ4uqm5R6SOn8pBYci5FtRJOl5X53LgfZP6jDSFRzvsNRb AqCng9dzoPE8U7OlzHAE3pB05STFWs0eE49/RyTVp5RDEpT6znfC9+1yYkxANs1vFN 9OLw0jdWTTD0A== Date: Tue, 7 Nov 2023 10:38:09 +0000 From: Will Deacon To: Vincent Guittot Cc: linux@armlinux.org.uk, catalin.marinas@arm.com, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, sudeep.holla@arm.com, gregkh@linuxfoundation.org, rafael@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, viresh.kumar@linaro.org, lenb@kernel.org, robert.moore@intel.com, lukasz.luba@arm.com, ionela.voinescu@arm.com, pierre.gondois@arm.com, beata.michalska@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-pm@vger.kernel.org, linux-acpi@vger.kernel.org, conor.dooley@microchip.com, suagrfillet@gmail.com, ajones@ventanamicro.com, lftan@kernel.org Subject: Re: [PATCH v5 7/7] arm64/amu: Use capacity_ref_freq to set AMU ratio Message-ID: <20231107103808.GF18944@willie-the-truck> References: <20231104105907.1365392-1-vincent.guittot@linaro.org> <20231104105907.1365392-8-vincent.guittot@linaro.org> Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231104105907.1365392-8-vincent.guittot@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) On Sat, Nov 04, 2023 at 11:59:07AM +0100, Vincent Guittot wrote: > Use the new capacity_ref_freq to set the ratio that is used by AMU for > computing the arch_scale_freq_capacity(). > This helps to keep everything aligned using the same reference for > computing CPUs capacity. > > The default value of the ratio (stored in per_cpu(arch_max_freq_scale)) > ensures that arch_scale_freq_capacity() returns max capacity until it is > set to its correct value with the cpu capacity and capacity_ref_freq. > > Signed-off-by: Vincent Guittot > --- > arch/arm64/kernel/topology.c | 26 ++++++++++++++------------ > drivers/base/arch_topology.c | 12 +++++++++++- > include/linux/arch_topology.h | 1 + > 3 files changed, 26 insertions(+), 13 deletions(-) > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > index 817d788cd866..615c1a20129f 100644 > --- a/arch/arm64/kernel/topology.c > +++ b/arch/arm64/kernel/topology.c > @@ -82,7 +82,12 @@ int __init parse_acpi_topology(void) > #undef pr_fmt > #define pr_fmt(fmt) "AMU: " fmt > > -static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale); > +/* > + * Ensure that amu_scale_freq_tick() will return SCHED_CAPACITY_SCALE until > + * the CPU capacity and its associated frequency have been correctly > + * initialized. > + */ > +static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) = 1UL << (2 * SCHED_CAPACITY_SHIFT); This doesn't seem to match the comment? SCHED_CAPACITY_SCALE doesn't have the '2 *' multiplier. > static DEFINE_PER_CPU(u64, arch_const_cycles_prev); > static DEFINE_PER_CPU(u64, arch_core_cycles_prev); > static cpumask_var_t amu_fie_cpus; > @@ -112,14 +117,14 @@ static inline bool freq_counters_valid(int cpu) > return true; > } > > -static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate) > +void freq_inv_set_max_ratio(int cpu, u64 max_rate) > { > - u64 ratio; > + u64 ratio, ref_rate = arch_timer_get_rate(); > > if (unlikely(!max_rate || !ref_rate)) { > - pr_debug("CPU%d: invalid maximum or reference frequency.\n", > + WARN_ONCE(1, "CPU%d: invalid maximum or reference frequency.\n", > cpu); > - return -EINVAL; > + return; > } > > /* > @@ -139,12 +144,12 @@ static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate) > ratio = div64_u64(ratio, max_rate); > if (!ratio) { > WARN_ONCE(1, "Reference frequency too low.\n"); > - return -EINVAL; > + return; > } > > - per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio; > + WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio); Why is WRITE_ONCE() now needed? > - return 0; > + return; Pointless 'return;' statement. Will