[PATCH][ ARM cpu hotplug 2/2 ] Use common cpu hotplug code for UX500

[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 stericsson.com>
---
 arch/arm/Kconfig              |    1 +
 arch/arm/mach-ux500/Makefile  |    2 +-
 arch/arm/mach-ux500/hotplug.c |   68 +++++++++-------------------------------
 arch/arm/mach-ux500/platsmp.c |    2 +
 4 files changed, 20 insertions(+), 53 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ca96a44..ee74cf9 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -797,6 +797,7 @@ config ARCH_U8500
       select GENERIC_CLOCKEVENTS
       select COMMON_CLKDEV
       select ARCH_REQUIRE_GPIOLIB
+       select USE_COMMON_ARM_HOTPLUG if HOTPLUG_CPU
       help
         Support for ST-Ericsson's Ux500 architecture

diff --git a/arch/arm/mach-ux500/Makefile b/arch/arm/mach-ux500/Makefile
index 0612013..cb86197 100644
--- a/arch/arm/mach-ux500/Makefile
+++ b/arch/arm/mach-ux500/Makefile
@@ -8,7 +8,7 @@ obj-$(CONFIG_UX500_SOC_DB8500)  += cpu-db8500.o
devices-db8500.o prcmu.o
 obj-$(CONFIG_MACH_U8500_MOP)   += board-mop500.o board-mop500-sdi.o
 obj-$(CONFIG_MACH_U5500)       += board-u5500.o
 obj-$(CONFIG_SMP)              += platsmp.o headsmp.o
-obj-$(CONFIG_HOTPLUG_CPU)      += hotplug.o
+obj-$(CONFIG_USE_COMMON_ARM_HOTPLUG)   += hotplug.o
 obj-$(CONFIG_LOCAL_TIMERS)     += localtimer.o
 obj-$(CONFIG_REGULATOR_AB8500) += board-mop500-regulators.o
 obj-$(CONFIG_U5500_MODEM_IRQ)  += modem_irq.o
diff --git a/arch/arm/mach-ux500/hotplug.c b/arch/arm/mach-ux500/hotplug.c
index b782a03..14a614f 100644
--- a/arch/arm/mach-ux500/hotplug.c
+++ b/arch/arm/mach-ux500/hotplug.c
@@ -6,70 +6,34 @@
 *     Based on ARM realview platform
 *
 * Author: Sundar Iyer <sundar.iyer at stericsson.com>
+ * Author: Vincent Guittot <vincent.guittot at stericsson.com>
 *
+ * We only keep platform related code in the subarchitecture directory.
+ * The common code across platform has been moved into kernel/common directory
 */
-#include <linux/kernel.h>
-#include <linux/errno.h>
-#include <linux/smp.h>
-#include <linux/completion.h>

-#include <asm/cacheflush.h>
+#include <asm/hotplug.h>

 extern volatile int pen_release;

-static DECLARE_COMPLETION(cpu_killed);
-
-static inline void platform_do_lowpower(unsigned int cpu)
-{
-       flush_cache_all();
-
-       /* we put the platform to just WFI */
-       for (;;) {
-               __asm__ __volatile__("dsb\n\t" "wfi\n\t"
-                               : : : "memory");
-               if (pen_release == cpu) {
-                       /*
-                        * OK, proper wakeup, we're done
-                        */
-                       break;
-               }
-       }
-}
-
-int platform_cpu_kill(unsigned int cpu)
+/* Default implementation that will be used if not override
+ * by power specific implementation
+ */
+void __attribute__((weak)) platform_enter_lowpower(unsigned int cpu)
 {
-       return wait_for_completion_timeout(&cpu_killed, 5000);
+       return;
 }

-/*
- * platform-specific code to shutdown a CPU
- *
- * Called with IRQs disabled
- */
-void platform_cpu_die(unsigned int cpu)
+int __attribute__((weak)) platform_do_lowpower(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);
+       __asm__ __volatile__("dsb\n\t" "wfi\n\t"
+                               : : : "memory");

-       /* directly enter low power state, skipping secure registers */
-       platform_do_lowpower(cpu);
+       return pen_release;
 }

-int platform_cpu_disable(unsigned int cpu)
+void __attribute__((weak)) platform_leave_lowpower(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;
+       return;
 }
+
diff --git a/arch/arm/mach-ux500/platsmp.c b/arch/arm/mach-ux500/platsmp.c
index 9e4c678..3074260 100644
--- a/arch/arm/mach-ux500/platsmp.c
+++ b/arch/arm/mach-ux500/platsmp.c
@@ -51,6 +51,7 @@ void __cpuinit platform_secondary_init(unsigned int cpu)
        * pen, then head off into the C entry point
        */
       pen_release = -1;
+       smp_wmb();

       /*
        * Synchronise with the boot thread.
@@ -82,6 +83,7 @@ int __cpuinit boot_secondary(unsigned int cpu,
struct task_struct *idle)

       timeout = jiffies + (1 * HZ);
       while (time_before(jiffies, timeout)) {
+               smp_rmb();
               if (pen_release == -1)
                       break;
       }
--
1.7.0.4