1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 *  Copyright (C) 2002 ARM Ltd.
  4 *  All Rights Reserved
  5 *
  6 * This hotplug implementation is _specific_ to the situation found on
  7 * ARM development platforms where there is _no_ possibility of actually
  8 * taking a CPU offline, resetting it, or otherwise.  Real platforms must
  9 * NOT copy this code.
 10 */
 11#include <linux/kernel.h>
 12#include <linux/errno.h>
 13#include <linux/smp.h>
 14
 15#include <asm/smp_plat.h>
 16#include <asm/cp15.h>
 17
 18#include <plat/platsmp.h>
 19
 20static inline void versatile_immitation_enter_lowpower(unsigned int actrl_mask)
 21{
 22	unsigned int v;
 23
 24	asm volatile(
 25		"mcr	p15, 0, %1, c7, c5, 0\n"
 26	"	mcr	p15, 0, %1, c7, c10, 4\n"
 27	/*
 28	 * Turn off coherency
 29	 */
 30	"	mrc	p15, 0, %0, c1, c0, 1\n"
 31	"	bic	%0, %0, %3\n"
 32	"	mcr	p15, 0, %0, c1, c0, 1\n"
 33	"	mrc	p15, 0, %0, c1, c0, 0\n"
 34	"	bic	%0, %0, %2\n"
 35	"	mcr	p15, 0, %0, c1, c0, 0\n"
 36	  : "=&r" (v)
 37	  : "r" (0), "Ir" (CR_C), "Ir" (actrl_mask)
 38	  : "cc");
 39}
 40
 41static inline void versatile_immitation_leave_lowpower(unsigned int actrl_mask)
 42{
 43	unsigned int v;
 44
 45	asm volatile(
 46		"mrc	p15, 0, %0, c1, c0, 0\n"
 47	"	orr	%0, %0, %1\n"
 48	"	mcr	p15, 0, %0, c1, c0, 0\n"
 49	"	mrc	p15, 0, %0, c1, c0, 1\n"
 50	"	orr	%0, %0, %2\n"
 51	"	mcr	p15, 0, %0, c1, c0, 1\n"
 52	  : "=&r" (v)
 53	  : "Ir" (CR_C), "Ir" (actrl_mask)
 54	  : "cc");
 55}
 56
 57static inline void versatile_immitation_do_lowpower(unsigned int cpu, int *spurious)
 58{
 59	/*
 60	 * there is no power-control hardware on this platform, so all
 61	 * we can do is put the core into WFI; this is safe as the calling
 62	 * code will have already disabled interrupts.
 63	 *
 64	 * This code should not be used outside Versatile platforms.
 65	 */
 66	for (;;) {
 67		wfi();
 68
 69		if (versatile_cpu_release == cpu_logical_map(cpu)) {
 70			/*
 71			 * OK, proper wakeup, we're done
 72			 */
 73			break;
 74		}
 75
 76		/*
 77		 * Getting here, means that we have come out of WFI without
 78		 * having been woken up - this shouldn't happen
 79		 *
 80		 * Just note it happening - when we're woken, we can report
 81		 * its occurrence.
 82		 */
 83		(*spurious)++;
 84	}
 85}
 86
 87/*
 88 * platform-specific code to shutdown a CPU.
 89 * This code supports immitation-style CPU hotplug for Versatile/Realview/
 90 * Versatile Express platforms that are unable to do real CPU hotplug.
 91 */
 92void versatile_immitation_cpu_die(unsigned int cpu, unsigned int actrl_mask)
 93{
 94	int spurious = 0;
 95
 96	versatile_immitation_enter_lowpower(actrl_mask);
 97	versatile_immitation_do_lowpower(cpu, &spurious);
 98	versatile_immitation_leave_lowpower(actrl_mask);
 99
100	if (spurious)
101		pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
102}