linux-kernel - [PATCH v2 1/2] LoongArch: Remove clock setting during cpu hotplug stage

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Date:   Tue, 26 Jul 2022 17:40:48 +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 v2 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 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 accessing in
generic loongarch cpu hotplug flow.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
Reviewed-by:   WANG Xuerui <git@...0n.name>
---
 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