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// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/arch/arm/plat-versatile/platsmp.c
*
* 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 <plat/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);
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);
}
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;
}
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