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diff --git a/arch/arm/mach-versatile/platsmp.c b/arch/arm/mach-versatile/platsmp.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);
+
+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;
+}