[PATCH 52/74] ST SPEAr13xx: Adding CPU hotplug support added for SMP platforms

[Viresh KUMAR]

From: Deepak Sikri <deepak.sikri at st.com>

Signed-off-by: Deepak Sikri <deepak.sikri at st.com>
Signed-off-by: shiraz hashim <shiraz.hashim at st.com>
Signed-off-by: Viresh Kumar <viresh.kumar at st.com>
---
 arch/arm/mach-spear13xx/Makefile  |    1 +
 arch/arm/mach-spear13xx/hotplug.c |  146 +++++++++++++++++++++++++++++++++++++
 arch/arm/mach-spear13xx/platsmp.c |   12 +++
 3 files changed, 159 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/mach-spear13xx/hotplug.c

diff --git a/arch/arm/mach-spear13xx/Makefile b/arch/arm/mach-spear13xx/Makefile
index b786edc..b092231 100644
--- a/arch/arm/mach-spear13xx/Makefile
+++ b/arch/arm/mach-spear13xx/Makefile
@@ -18,3 +18,4 @@ obj-$(CONFIG_MACH_SPEAR1310)		+= spear1310.o
 # spear1310 boards files
 obj-$(CONFIG_BOARD_SPEAR1310_EVB)	+= spear1310_evb.o
 obj-$(CONFIG_PM)	+= pm.o sleep.o
+obj-$(CONFIG_HOTPLUG_CPU)		+= hotplug.o
diff --git a/arch/arm/mach-spear13xx/hotplug.c b/arch/arm/mach-spear13xx/hotplug.c
new file mode 100644
index 0000000..6405e49
--- /dev/null
+++ b/arch/arm/mach-spear13xx/hotplug.c
@@ -0,0 +1,146 @@
+/*
+ * linux/arch/arm/mach-spear13xx/hotplug.c
+ *
+ * Copyright (C) 2010 ST Microelectronics Ltd.
+ * Deepak Sikri <deepak.sikri at st.com>
+ *
+ * based upon 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>
+
+#include <asm/cacheflush.h>
+
+extern volatile int pen_release;
+
+static DECLARE_COMPLETION(cpu_killed);
+
+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, #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
+		pr_crit("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 __cpuinit platform_cpu_die(unsigned int cpu)
+{
+#ifdef DEBUG
+	unsigned int this_cpu = hard_smp_processor_id();
+
+	if (cpu != this_cpu) {
+		pr_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 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;
+}
diff --git a/arch/arm/mach-spear13xx/platsmp.c b/arch/arm/mach-spear13xx/platsmp.c
index 73fbcdb..2864a5c 100644
--- a/arch/arm/mach-spear13xx/platsmp.c
+++ b/arch/arm/mach-spear13xx/platsmp.c
@@ -101,6 +101,18 @@ int __cpuinit boot_secondary(unsigned int cpu, struct task_struct *idle)
 	pen_release = cpu;
 	flush_cache_all();
 
+	/*
+	 * XXX
+	 *
+	 * This is a later addition to the booting protocol: the
+	 * bootMonitor now puts secondary cores into WFI, so
+	 * poke_milo() no longer gets the cores moving; we need
+	 * to send a soft interrupt to wake the secondary core.
+	 * Use smp_cross_call() for this, since there's little
+	 * point duplicating the code here
+	 */
+	smp_cross_call(cpumask_of(cpu));
+
 	timeout = jiffies + (1 * HZ);
 	while (time_before(jiffies, timeout)) {
 		smp_rmb();
-- 
1.7.2.2