linux-kernel - [PATCH 1/2] LoongArch: Remove clock setting during cpu hotplug stage

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Date:   Wed, 20 Jul 2022 15:21:51 +0800
From:   Bibo Mao <maobibo@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     WANG Xuerui <kernel@...0n.name>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] LoongArch: Remove clock setting during cpu hotplug stage

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.

Signed-off-by: Bibo Mao <maobibo@...ngson.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,
-- 
2.31.1