[PATCH][ ARM cpu hotplug 1/2 ] extract common code for arm cpu hotplug

[Vincent Guittot]

This patch extracts the common code of the cpu hotplug feature across
arm platforms. The goal is to only keep the specific stuff of the
platform in the sub-architecture. I have created a hotplug.c file in
the  arm/common directory after studying the cpu hotplug code of
omap2, realview, s5pv310, ux500 and tegra. I have extracted 3 main
platform dependent functions:
 -platform_enter_lowpower which prepares the platform for low power.
 -platform_do_lowpower on which the cpu will loop until it becomes
really plugged (spurious wake up). This function must returned the cpu
Id in order to leave the unplug state.
 -platform_leave_lowpower which restore the platform context.

 An ux500 patch is available which uses the common/hotplug.c code.
This patch is quite short because the idle / power down functions are
not yet upstreamed


Signed-off-by: Vincent Guittot <vincent.guittot at linaro.org>
---
 arch/arm/common/Kconfig        |    4 ++
 arch/arm/common/Makefile       |    1 +
 arch/arm/common/hotplug.c      |   85 ++++++++++++++++++++++++++++++++++++++++
 arch/arm/include/asm/hotplug.h |    8 ++++
 4 files changed, 98 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/common/hotplug.c
 create mode 100644 arch/arm/include/asm/hotplug.h

diff --git a/arch/arm/common/Kconfig b/arch/arm/common/Kconfig
index 0a34c81..b1c5f6b 100644
--- a/arch/arm/common/Kconfig
+++ b/arch/arm/common/Kconfig
@@ -41,3 +41,7 @@ config SHARP_SCOOP
 config COMMON_CLKDEV
       bool
       select HAVE_CLK
+
+config USE_COMMON_ARM_HOTPLUG
+       bool
+       depends on HOTPLUG_CPU
diff --git a/arch/arm/common/Makefile b/arch/arm/common/Makefile
index e6e8664..d8a66d7 100644
--- a/arch/arm/common/Makefile
+++ b/arch/arm/common/Makefile
@@ -17,3 +17,4 @@ obj-$(CONFIG_ARCH_IXP2000)    += uengine.o
 obj-$(CONFIG_ARCH_IXP23XX)     += uengine.o
 obj-$(CONFIG_PCI_HOST_ITE8152)  += it8152.o
 obj-$(CONFIG_COMMON_CLKDEV)    += clkdev.o
+obj-$(CONFIG_USE_COMMON_ARM_HOTPLUG)           += hotplug.o
diff --git a/arch/arm/common/hotplug.c b/arch/arm/common/hotplug.c
new file mode 100644
index 0000000..05f39f9
--- /dev/null
+++ b/arch/arm/common/hotplug.c
@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) STMicroelectronics 2009
+ * Copyright (C) ST-Ericsson SA 2010
+ *
+ * License Terms: GNU General Public License v2
+ *     Based on ARM realview platform
+ *
+ * Author: Sundar Iyer <sundar.iyer at stericsson.com>
+ * Author: Vincent Guittot <vincent.guittot at stericsson.com>
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/smp.h>
+#include <linux/completion.h>
+
+#include <asm/cacheflush.h>
+#include <asm/hotplug.h>
+
+static DECLARE_COMPLETION(cpu_killed);
+
+int platform_cpu_kill(unsigned int cpu)
+{
+       int err;
+       err = wait_for_completion_timeout(&cpu_killed, 5000);
+#ifdef DEBUG
+       printk(KERN_INFO "platform_cpu_kill %d err %d\n", cpu, err);
+#endif
+       return err;
+}
+
+/*
+ * architecture-specific code to shutdown a CPU
+ *
+ * Called with IRQs disabled
+ */
+void platform_cpu_die(unsigned int cpu)
+{
+       unsigned long spurious = 0;
+#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();
+       }
+
+       printk(KERN_NOTICE "CPU%u: shutdown\n", cpu);
+#endif
+       complete(&cpu_killed);
+
+       flush_cache_all();
+       wmb();
+
+       platform_enter_lowpower(cpu);
+
+       for (;;) {
+
+               if (platform_do_lowpower(cpu) == cpu) {
+                       /*
+                        * OK, proper wakeup, we're done
+                        */
+                       break;
+               }
+               spurious++;
+       }
+
+       platform_leave_lowpower(cpu);
+
+#ifdef DEBUG
+       printk(KERN_NOTICE "CPU%u: wake up (%lu spurious wake up)\n",
+                       cpu, spurious);
+#endif
+
+}
+
+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/include/asm/hotplug.h b/arch/arm/include/asm/hotplug.h
new file mode 100644
index 0000000..b38e737
--- /dev/null
+++ b/arch/arm/include/asm/hotplug.h
@@ -0,0 +1,8 @@
+#ifndef __ASM_MACH_HOTPLUG_H
+#define __ASM_MACH_HOTPLUG_H
+
+extern void platform_enter_lowpower(unsigned int cpu);
+extern int platform_do_lowpower(unsigned int cpu);
+extern void platform_leave_lowpower(unsigned int cpu);
+
+#endif
--
1.7.0.4