From e9882777d992b76e0b80deadd66ad886c25f5d1f Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Sun, 19 Dec 2010 11:33:12 +0000
Subject: [PATCH] ARM: CPU hotplug: add Versatile Express hotplug CPU support
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
arch/arm/mach-vexpress/Makefile | 1 +
arch/arm/mach-vexpress/hotplug.c | 128 +++++++++++++++++++++++++++++++
2 files changed, 129 insertions(+)
create mode 100644 arch/arm/mach-vexpress/hotplug.c
diff --git a/arch/arm/mach-vexpress/Makefile b/arch/arm/mach-vexpress/Makefile
index 1b71b77ade2297..2c0ac7de28142d 100644
--- a/arch/arm/mach-vexpress/Makefile
+++ b/arch/arm/mach-vexpress/Makefile
@@ -5,4 +5,5 @@
obj-y := v2m.o
obj-$(CONFIG_ARCH_VEXPRESS_CA9X4) += ct-ca9x4.o
obj-$(CONFIG_SMP) += platsmp.o headsmp.o
+obj-$(CONFIG_HOTPLUG_CPU) += hotplug.o
obj-$(CONFIG_LOCAL_TIMERS) += localtimer.o
diff --git a/arch/arm/mach-vexpress/hotplug.c b/arch/arm/mach-vexpress/hotplug.c
new file mode 100644
index 00000000000000..ea4cbfb90a6673
--- /dev/null
+++ b/arch/arm/mach-vexpress/hotplug.c
@@ -0,0 +1,128 @@
+/*
+ * linux/arch/arm/mach-realview/hotplug.c
+ *
+ * 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/cacheflush.h>
+
+extern volatile int pen_release;
+
+static inline void cpu_enter_lowpower(void)
+{
+ unsigned int v;
+
+ flush_cache_all();
+ 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, %3\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), "Ir" (0x40)
+ : "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, %2\n"
+ " mcr p15, 0, %0, c1, c0, 1\n"
+ : "=&r" (v)
+ : "Ir" (CR_C), "Ir" (0x40)
+ : "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) {
+ /*
+ * 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)++;
+ }
+}
+
+int platform_cpu_kill(unsigned int cpu)
+{
+ return 1;
+}
+
+/*
+ * platform-specific code to shutdown a CPU
+ *
+ * Called with IRQs disabled
+ */
+void platform_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);
+}
+
+int platform_cpu_disable(unsigned int cpu)
+{
+ /*
+ * we don't allow CPU 0 to be shutdown (it is still too special
+ * e.g. clock tick interrupts)
+ */
+ return cpu == 0 ? -EPERM : 0;
+}
--
GitLab