alistair23-linux/arch/arm/mach-spear/hotplug.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * linux/arch/arm/mach-spear13xx/hotplug.c
 *
 * Copyright (C) 2012 ST Microelectronics Ltd.
 * Deepak Sikri <deepak.sikri@st.com>
 *
 * based upon linux/arch/arm/mach-realview/hotplug.c
 */
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/smp.h>
#include <asm/cp15.h>
#include <asm/smp_plat.h>

#include "generic.h"

static inline void cpu_enter_lowpower(void)
{
	unsigned int v;

	asm volatile(
	"	mcr	p15, 0, %1, c7, c5, 0\n"
	"	dsb\n"
	/*
	 * Turn off coherency
	 */
	"	mrc	p15, 0, %0, c1, c0, 1\n"
	"	bic	%0, %0, #0x20\n"
	"	mcr	p15, 0, %0, c1, c0, 1\n"
	"	mrc	p15, 0, %0, c1, c0, 0\n"
	"	bic	%0, %0, %2\n"
	"	mcr	p15, 0, %0, c1, c0, 0\n"
	: "=&r" (v)
	: "r" (0), "Ir" (CR_C)
	: "cc", "memory");
}

static inline void cpu_leave_lowpower(void)
{
	unsigned int v;

	asm volatile("mrc	p15, 0, %0, c1, c0, 0\n"
	"	orr	%0, %0, %1\n"
	"	mcr	p15, 0, %0, c1, c0, 0\n"
	"	mrc	p15, 0, %0, c1, c0, 1\n"
	"	orr	%0, %0, #0x20\n"
	"	mcr	p15, 0, %0, c1, c0, 1\n"
	: "=&r" (v)
	: "Ir" (CR_C)
	: "cc");
}

static inline void spear13xx_do_lowpower(unsigned int cpu, int *spurious)
{
	for (;;) {
		wfi();

		if (spear_pen_release == cpu) {
			/*
			 * OK, proper wakeup, we're done
			 */
			break;
		}

		/*
		 * Getting here, means that we have come out of WFI without
		 * having been woken up - this shouldn't happen
		 *
		 * Just note it happening - when we're woken, we can report
		 * its occurrence.
		 */
		(*spurious)++;
	}
}

/*
 * platform-specific code to shutdown a CPU
 *
 * Called with IRQs disabled
 */
void spear13xx_cpu_die(unsigned int cpu)
{
	int spurious = 0;

	/*
	 * we're ready for shutdown now, so do it
	 */
	cpu_enter_lowpower();
	spear13xx_do_lowpower(cpu, &spurious);

	/*
	 * bring this CPU back into the world of cache
	 * coherency, and then restore interrupts
	 */
	cpu_leave_lowpower();

	if (spurious)
		pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
}