[ARM SMP] Add CPU hotplug support for Realview MPcore

Add platform specific parts for hotplug CPU support for the
Realview board.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 139 insertions, 0 deletions

diff --git a/arch/arm/mach-realview/Makefile b/arch/arm/mach-realview/Makefile
index a6a40dac26a9..36e76ba937fc 100644
--- a/arch/arm/mach-realview/Makefile
+++ b/arch/arm/mach-realview/Makefile
@@ -5,4 +5,5 @@
 obj-y                                   := core.o clock.o
 obj-$(CONFIG_MACH_REALVIEW_EB)          += realview_eb.o
 obj-$(CONFIG_SMP)                       += platsmp.o headsmp.o
+obj-$(CONFIG_HOTPLUG_CPU)               += hotplug.o
 obj-$(CONFIG_LOCAL_TIMERS)              += localtimer.o
diff --git a/arch/arm/mach-realview/hotplug.c b/arch/arm/mach-realview/hotplug.c
new file mode 100644
index 000000000000..09748cbcd10e
--- /dev/null
+++ b/arch/arm/mach-realview/hotplug.c
@@ -0,0 +1,138 @@
+/*
+ *  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 <linux/completion.h>
+
+extern volatile int pen_release;
+
+static DECLARE_COMPLETION(cpu_killed);
+
+static inline void cpu_enter_lowpower(void)
+{
+        unsigned int v;
+
+        asm volatile(   "mcr    p15, 0, %1, c7, c14, 0\n"
+        "       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, #0x04\n"
+        "       mcr     p15, 0, %0, c1, c0, 0\n"
+          : "=&r" (v)
+          : "r" (0)
+          : "cc");
+}
+
+static inline void cpu_leave_lowpower(void)
+{
+        unsigned int v;
+
+        asm volatile(   "mrc    p15, 0, %0, c1, c0, 0\n"
+        "       orr     %0, %0, #0x04\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)
+          :
+          : "cc");
+}
+
+static inline void platform_do_lowpower(unsigned int cpu)
+{
+        /*
+         * 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
+                 *
+                 * The trouble is, letting people know about this is not really
+                 * possible, since we are currently running incoherently, and
+                 * therefore cannot safely call printk() or anything else
+                 */
+#ifdef DEBUG
+                printk("CPU%u: spurious wakeup call\n", cpu);
+#endif
+        }
+}
+
+int platform_cpu_kill(unsigned int cpu)
+{
+        return wait_for_completion_timeout(&cpu_killed, 5000);
+}
+
+/*
+ * platform-specific code to shutdown a CPU
+ *
+ * Called with IRQs disabled
+ */
+void platform_cpu_die(unsigned int cpu)
+{
+#ifdef DEBUG
+        unsigned int this_cpu = hard_smp_processor_id();
+
+        if (cpu != this_cpu) {
+                printk(KERN_CRIT "Eek! platform_cpu_die running on %u, should be %u\n",
+                           this_cpu, cpu);
+                BUG();
+        }
+#endif
+
+        printk(KERN_NOTICE "CPU%u: shutdown\n", cpu);
+        complete(&cpu_killed);
+
+        /*
+         * we're ready for shutdown now, so do it
+         */
+        cpu_enter_lowpower();
+        platform_do_lowpower(cpu);
+
+        /*
+         * bring this CPU back into the world of cache
+         * coherency, and then restore interrupts
+         */
+        cpu_leave_lowpower();
+}
+
+int mach_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;
+}