103 lines
2.5 KiB
C
103 lines
2.5 KiB
C
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2002 ARM Ltd.
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* All Rights Reserved
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*
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* This hotplug implementation is _specific_ to the situation found on
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* ARM development platforms where there is _no_ possibility of actually
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* taking a CPU offline, resetting it, or otherwise. Real platforms must
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* NOT copy this code.
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*/
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/smp.h>
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#include <asm/smp_plat.h>
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#include <asm/cp15.h>
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#include "platsmp.h"
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static inline void versatile_immitation_enter_lowpower(unsigned int actrl_mask)
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{
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unsigned int v;
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asm volatile(
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"mcr p15, 0, %1, c7, c5, 0\n"
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" mcr p15, 0, %1, c7, c10, 4\n"
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/*
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* Turn off coherency
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*/
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" mrc p15, 0, %0, c1, c0, 1\n"
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" bic %0, %0, %3\n"
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" mcr p15, 0, %0, c1, c0, 1\n"
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" mrc p15, 0, %0, c1, c0, 0\n"
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" bic %0, %0, %2\n"
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" mcr p15, 0, %0, c1, c0, 0\n"
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: "=&r" (v)
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: "r" (0), "Ir" (CR_C), "Ir" (actrl_mask)
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: "cc");
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}
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static inline void versatile_immitation_leave_lowpower(unsigned int actrl_mask)
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{
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unsigned int v;
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asm volatile(
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"mrc p15, 0, %0, c1, c0, 0\n"
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" orr %0, %0, %1\n"
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" mcr p15, 0, %0, c1, c0, 0\n"
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" mrc p15, 0, %0, c1, c0, 1\n"
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" orr %0, %0, %2\n"
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" mcr p15, 0, %0, c1, c0, 1\n"
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: "=&r" (v)
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: "Ir" (CR_C), "Ir" (actrl_mask)
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: "cc");
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}
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static inline void versatile_immitation_do_lowpower(unsigned int cpu, int *spurious)
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{
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/*
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* there is no power-control hardware on this platform, so all
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* we can do is put the core into WFI; this is safe as the calling
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* code will have already disabled interrupts.
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*
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* This code should not be used outside Versatile platforms.
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*/
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for (;;) {
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wfi();
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if (versatile_cpu_release == cpu_logical_map(cpu)) {
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/*
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* OK, proper wakeup, we're done
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*/
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break;
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}
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/*
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* Getting here, means that we have come out of WFI without
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* having been woken up - this shouldn't happen
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*
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* Just note it happening - when we're woken, we can report
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* its occurrence.
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*/
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(*spurious)++;
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}
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}
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/*
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* platform-specific code to shutdown a CPU.
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* This code supports immitation-style CPU hotplug for Versatile/Realview/
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* Versatile Express platforms that are unable to do real CPU hotplug.
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*/
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void versatile_immitation_cpu_die(unsigned int cpu, unsigned int actrl_mask)
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{
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int spurious = 0;
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versatile_immitation_enter_lowpower(actrl_mask);
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versatile_immitation_do_lowpower(cpu, &spurious);
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versatile_immitation_leave_lowpower(actrl_mask);
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if (spurious)
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pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
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}
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