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ARM: oxnas: remove CPU hotplug implementation

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The CPU hotplug implementation on this platform is cargo-culted from
the plat-versatile implementation, and is buggy.  Once a CPU hits the
"low power" loop, it will wait for pen_release to be set to the CPU
number to wake up again - but nothing in this implementation does that.

So, once a CPU has entered cpu_die() it will never, ever leave.

Remove this useless cargo-culted implementation.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Russell King 2018-12-13 12:54:26 +00:00
parent d0e22329e1
commit 0eb037998a
3 changed files with 0 additions and 114 deletions
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1
arch/arm/mach-oxnas/Makefile
View File

@ -1,2 +1 @@
obj-$(CONFIG_SMP) += platsmp.o headsmp.o
obj-$(CONFIG_HOTPLUG_CPU) += hotplug.o

109
arch/arm/mach-oxnas/hotplug.c
View File

@ -1,109 +0,0 @@
/*
* Copyright (C) 2002 ARM Ltd.
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/smp.h>
#include <asm/cp15.h>
#include <asm/smp_plat.h>
static inline void cpu_enter_lowpower(void)
{
unsigned int v;
asm volatile(
" mcr p15, 0, %1, c7, c5, 0\n"
" mcr p15, 0, %1, c7, c10, 4\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");
}
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 platform_do_lowpower(unsigned int cpu, int *spurious)
{
/*
* there is no power-control hardware on this platform, so all
* we can do is put the core into WFI; this is safe as the calling
* code will have already disabled interrupts
*/
for (;;) {
/*
* here's the WFI
*/
asm(".word 0xe320f003\n"
:
:
: "memory", "cc");
if (pen_release == cpu_logical_map(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 ox820_cpu_die(unsigned int cpu)
{
int spurious = 0;
/*
* we're ready for shutdown now, so do it
*/
cpu_enter_lowpower();
platform_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);
}

4
arch/arm/mach-oxnas/platsmp.c
View File

@ -19,7 +19,6 @@
#include <asm/smp_scu.h>
extern void ox820_secondary_startup(void);
extern void ox820_cpu_die(unsigned int cpu);
static void __iomem *cpu_ctrl;
static void __iomem *gic_cpu_ctrl;
@ -94,9 +93,6 @@ unmap_scu:
static const struct smp_operations ox820_smp_ops __initconst = {
.smp_prepare_cpus = ox820_smp_prepare_cpus,
.smp_boot_secondary = ox820_boot_secondary,
#ifdef CONFIG_HOTPLUG_CPU
.cpu_die = ox820_cpu_die,
#endif
};
CPU_METHOD_OF_DECLARE(ox820_smp, "oxsemi,ox820-smp", &ox820_smp_ops);