LoongArch: Remove clock setting during cpu hotplug stage

mainline inclusion
from mainline-v5.19
commit 71610ab1
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5OHOB
CVE: NA

--------------------------------

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.
Reviewed-by: NWANG Xuerui <git@xen0n.name>
Signed-off-by: NBibo Mao <maobibo@loongson.cn>
Signed-off-by: NHuacai Chen <chenhuacai@loongson.cn>

arch/loongarch/kernel/smp.c

@@ -278,116 +278,29 @@ void loongson3_cpu_die(unsigned int cpu)
 	mb();
 }
 
-/*
- * The target CPU should go to XKPRANGE (uncached area) and flush
- * ICache/DCache/VCache before the control CPU can safely disable its clock.
- */
-static void loongson3_play_dead(int *state_addr)
+void play_dead(void)
 {
-	register int val;
-	register void *addr;
+	register uint64_t addr;
 	register void (*init_fn)(void);
 
-	__asm__ __volatile__(
-		"   li.d %[addr], 0x8000000000000000\n"
-		"1: cacop 0x8, %[addr], 0           \n" /* flush ICache */
-		"   cacop 0x8, %[addr], 1           \n"
-		"   cacop 0x8, %[addr], 2           \n"
-		"   cacop 0x8, %[addr], 3           \n"
-		"   cacop 0x9, %[addr], 0           \n" /* flush DCache */
-		"   cacop 0x9, %[addr], 1           \n"
-		"   cacop 0x9, %[addr], 2           \n"
-		"   cacop 0x9, %[addr], 3           \n"
-		"   addi.w %[sets], %[sets], -1     \n"
-		"   addi.d %[addr], %[addr], 0x40   \n"
-		"   bnez %[sets], 1b                \n"
-		"   li.d %[addr], 0x8000000000000000\n"
-		"2: cacop 0xa, %[addr], 0           \n" /* flush VCache */
-		"   cacop 0xa, %[addr], 1           \n"
-		"   cacop 0xa, %[addr], 2           \n"
-		"   cacop 0xa, %[addr], 3           \n"
-		"   cacop 0xa, %[addr], 4           \n"
-		"   cacop 0xa, %[addr], 5           \n"
-		"   cacop 0xa, %[addr], 6           \n"
-		"   cacop 0xa, %[addr], 7           \n"
-		"   cacop 0xa, %[addr], 8           \n"
-		"   cacop 0xa, %[addr], 9           \n"
-		"   cacop 0xa, %[addr], 10          \n"
-		"   cacop 0xa, %[addr], 11          \n"
-		"   cacop 0xa, %[addr], 12          \n"
-		"   cacop 0xa, %[addr], 13          \n"
-		"   cacop 0xa, %[addr], 14          \n"
-		"   cacop 0xa, %[addr], 15          \n"
-		"   addi.w %[vsets], %[vsets], -1   \n"
-		"   addi.d %[addr], %[addr], 0x40   \n"
-		"   bnez   %[vsets], 2b             \n"
-		"   li.w   %[val], 0x7              \n" /* *state_addr = CPU_DEAD; */
-		"   st.w   %[val], %[state_addr], 0 \n"
-		"   dbar 0                          \n"
-		"   cacop 0x11, %[state_addr], 0    \n" /* flush entry of *state_addr */
-		: [addr] "=&r" (addr), [val] "=&r" (val)
-		: [state_addr] "r" (state_addr),
-		  [sets] "r" (cpu_data[smp_processor_id()].dcache.sets),
-		  [vsets] "r" (cpu_data[smp_processor_id()].vcache.sets));
-
+	idle_task_exit();
 	local_irq_enable();
-	change_csr_ecfg(ECFG0_IM, ECFGF_IPI);
+	set_csr_ecfg(ECFGF_IPI);
+	__this_cpu_write(cpu_state, CPU_DEAD);
+
+	__smp_mb();
+	do {
+		__asm__ __volatile__("idle 0\n\t");
+		addr = iocsr_read64(LOONGARCH_IOCSR_MBUF0);
+	} while (addr == 0);
 
-	__asm__ __volatile__(
-		"   idle      0			    \n"
-		"   li.w      $t0, 0x1020	    \n"
-		"   iocsrrd.d %[init_fn], $t0	    \n" /* Get init PC */
-		: [init_fn] "=&r" (addr)
-		: /* No Input */
-		: "a0");
-	init_fn = __va(addr);
+	init_fn = (void *)TO_CACHE(addr);
+	iocsr_write32(0xffffffff, LOONGARCH_IOCSR_IPI_CLEAR);
 
 	init_fn();
 	unreachable();
 }
 
-void play_dead(void)
-{
-	int *state_addr;
-	unsigned int cpu = smp_processor_id();
-	void (*play_dead_uncached)(int *s);
-
-	idle_task_exit();
-	play_dead_uncached = (void *)TO_UNCACHE(__pa((unsigned long)loongson3_play_dead));
-	state_addr = &per_cpu(cpu_state, cpu);
-	mb();
-	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
 
 /*

include/linux/cpuhotplug.h

@@ -91,7 +91,6 @@ 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,