From: WANG Xuerui <kernel@xen0n.name>
To: Bibo Mao <maobibo@loongson.cn>, Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
loongarch@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] LoongArch: Remove clock setting during cpu hotplug stage
Date: Fri, 22 Jul 2022 16:10:12 +0800 [thread overview]
Message-ID: <3324feed-e158-8c51-9915-85b0498f1888@xen0n.name> (raw)
In-Reply-To: <20220720072152.3894559-1-maobibo@loongson.cn>
On 2022/7/20 15:21, Bibo Mao wrote:
> On physical machine we can save power by disabling clock of hot removed cpu.
> However there will be problem, since different platforms have different clock
> setting methods, the code is platform relative. Also it can be in firmware/pmu
> compoments or cpu regulator driver, rather than general loongarch cpu booting
> flow.
>
> Also on qemu virt machine, device clock/freq setting is not
> emulated, there is no such registers.
>
> This patch removes hard-coded register accessing in generic
> loongarch cpu boot flow.
Improving a little on the wording (mostly fixing eyesore Chinglish):
"On physical machine we can save power by disabling clock of hot removed
cpu. However as different platforms require different methods to
configure clocks, the code is platform-specific, and probably belongs to
firmware/pmu or cpu regulator, rather than generic arch/loongarch code.
Also, there is no such register on QEMU virt machine since the
clock/frequency regulation is not emulated.
This patch removes the hard-coded clock register accesses in generic
loongarch cpu hotplug flow."
>
> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
> ---
> arch/loongarch/kernel/smp.c | 29 -----------------------------
> include/linux/cpuhotplug.h | 1 -
> 2 files changed, 30 deletions(-)
>
> diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
> index 73cec62504fb..98b3e059d344 100644
> --- a/arch/loongarch/kernel/smp.c
> +++ b/arch/loongarch/kernel/smp.c
> @@ -359,35 +359,6 @@ void play_dead(void)
> play_dead_uncached(state_addr);
> }
>
> -static int loongson3_enable_clock(unsigned int cpu)
> -{
> - uint64_t core_id = cpu_data[cpu].core;
> - uint64_t package_id = cpu_data[cpu].package;
> -
> - LOONGSON_FREQCTRL(package_id) |= 1 << (core_id * 4 + 3);
> -
> - return 0;
> -}
> -
> -static int loongson3_disable_clock(unsigned int cpu)
> -{
> - uint64_t core_id = cpu_data[cpu].core;
> - uint64_t package_id = cpu_data[cpu].package;
> -
> - LOONGSON_FREQCTRL(package_id) &= ~(1 << (core_id * 4 + 3));
> -
> - return 0;
> -}
> -
> -static int register_loongson3_notifier(void)
> -{
> - return cpuhp_setup_state_nocalls(CPUHP_LOONGARCH_SOC_PREPARE,
> - "loongarch/loongson:prepare",
> - loongson3_enable_clock,
> - loongson3_disable_clock);
> -}
> -early_initcall(register_loongson3_notifier);
> -
> #endif
>
> /*
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 19f0dbfdd7fe..b66c5f389159 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -130,7 +130,6 @@ enum cpuhp_state {
> CPUHP_ZCOMP_PREPARE,
> CPUHP_TIMERS_PREPARE,
> CPUHP_MIPS_SOC_PREPARE,
> - CPUHP_LOONGARCH_SOC_PREPARE,
> CPUHP_BP_PREPARE_DYN,
> CPUHP_BP_PREPARE_DYN_END = CPUHP_BP_PREPARE_DYN + 20,
> CPUHP_BRINGUP_CPU,
Seems good. I should have noticed earlier the fact the clock control
registers are, in every regard, model-specific, thus not appropriate for
arch/loongarch. Proper drivers should be added afterwards, though I
assume you must internally have something like that already.
Reviewed-by: WANG Xuerui <git@xen0n.name>
next prev parent reply other threads:[~2022-07-22 8:10 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-20 7:21 [PATCH 1/2] LoongArch: Remove clock setting during cpu hotplug stage Bibo Mao
2022-07-20 7:21 ` [PATCH 2/2] LoongArch: Remove unused variable Bibo Mao
2022-07-22 8:12 ` WANG Xuerui
2022-07-20 9:00 ` [PATCH 1/2] LoongArch: Remove clock setting during cpu hotplug stage Huacai Chen
2022-07-22 8:10 ` WANG Xuerui [this message]
2022-07-25 3:16 ` maobibo
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