WSL2-Linux-Kernel/arch/arm/mach-versatile/platsmp.c

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C
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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2002 ARM Ltd.
* All Rights Reserved
*
* This code is specific to the hardware found on ARM Realview and
* Versatile Express platforms where the CPUs are unable to be individually
* woken, and where there is no way to hot-unplug CPUs. Real platforms
* should not copy this code.
*/
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/jiffies.h>
#include <linux/smp.h>
#include <asm/cacheflush.h>
#include <asm/smp_plat.h>
#include "platsmp.h"
/*
* versatile_cpu_release controls the release of CPUs from the holding
* pen in headsmp.S, which exists because we are not always able to
* control the release of individual CPUs from the board firmware.
* Production platforms do not need this.
*/
volatile int versatile_cpu_release = -1;
/*
* Write versatile_cpu_release in a way that is guaranteed to be visible to
* all observers, irrespective of whether they're taking part in coherency
* or not. This is necessary for the hotplug code to work reliably.
*/
static void versatile_write_cpu_release(int val)
{
versatile_cpu_release = val;
smp_wmb();
sync_cache_w(&versatile_cpu_release);
}
/*
* versatile_lock exists to avoid running the loops_per_jiffy delay loop
* calibrations on the secondary CPU while the requesting CPU is using
* the limited-bandwidth bus - which affects the calibration value.
* Production platforms do not need this.
*/
static DEFINE_RAW_SPINLOCK(versatile_lock);
arm: delete __cpuinit/__CPUINIT usage from all ARM users The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. Note that some harmless section mismatch warnings may result, since notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c) and are flagged as __cpuinit -- so if we remove the __cpuinit from the arch specific callers, we will also get section mismatch warnings. As an intermediate step, we intend to turn the linux/init.h cpuinit related content into no-ops as early as possible, since that will get rid of these warnings. In any case, they are temporary and harmless. This removes all the ARM uses of the __cpuinit macros from C code, and all __CPUINIT from assembly code. It also had two ".previous" section statements that were paired off against __CPUINIT (aka .section ".cpuinit.text") that also get removed here. [1] https://lkml.org/lkml/2013/5/20/589 Cc: Russell King <linux@arm.linux.org.uk> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-17 23:43:14 +04:00
void versatile_secondary_init(unsigned int cpu)
{
/*
* let the primary processor know we're out of the
* pen, then head off into the C entry point
*/
versatile_write_cpu_release(-1);
/*
* Synchronise with the boot thread.
*/
raw_spin_lock(&versatile_lock);
raw_spin_unlock(&versatile_lock);
}
arm: delete __cpuinit/__CPUINIT usage from all ARM users The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. Note that some harmless section mismatch warnings may result, since notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c) and are flagged as __cpuinit -- so if we remove the __cpuinit from the arch specific callers, we will also get section mismatch warnings. As an intermediate step, we intend to turn the linux/init.h cpuinit related content into no-ops as early as possible, since that will get rid of these warnings. In any case, they are temporary and harmless. This removes all the ARM uses of the __cpuinit macros from C code, and all __CPUINIT from assembly code. It also had two ".previous" section statements that were paired off against __CPUINIT (aka .section ".cpuinit.text") that also get removed here. [1] https://lkml.org/lkml/2013/5/20/589 Cc: Russell King <linux@arm.linux.org.uk> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-17 23:43:14 +04:00
int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle)
{
unsigned long timeout;
/*
* Set synchronisation state between this boot processor
* and the secondary one
*/
raw_spin_lock(&versatile_lock);
/*
* This is really belt and braces; we hold unintended secondary
* CPUs in the holding pen until we're ready for them. However,
* since we haven't sent them a soft interrupt, they shouldn't
* be there.
*/
versatile_write_cpu_release(cpu_logical_map(cpu));
/*
* Send the secondary CPU a soft interrupt, thereby causing
* the boot monitor to read the system wide flags register,
* and branch to the address found there.
*/
arch_send_wakeup_ipi_mask(cpumask_of(cpu));
timeout = jiffies + (1 * HZ);
while (time_before(jiffies, timeout)) {
smp_rmb();
if (versatile_cpu_release == -1)
break;
udelay(10);
}
/*
* now the secondary core is starting up let it run its
* calibrations, then wait for it to finish
*/
raw_spin_unlock(&versatile_lock);
return versatile_cpu_release != -1 ? -ENOSYS : 0;
}