From: James Hogan <james.hogan@xxxxxxxxxx>
Add a CPU power management notifier callback for preserving general CPU
context. The CPU PM callbacks will be triggered by the powering down of
CPU cores, for example by cpuidle drivers & in the future by suspend to
RAM implementations.
The current state preserved is mostly related to the process context:
- FPU
- DSP
- ASID
- UserLocal
- Watch registers
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
---
arch/mips/Kconfig | 1 +
arch/mips/kernel/Makefile | 2 +
arch/mips/kernel/pm.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 98 insertions(+)
create mode 100644 arch/mips/kernel/pm.c
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 5cd695f..322bbe1 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -50,6 +50,7 @@ config MIPS
select CLONE_BACKWARDS
select HAVE_DEBUG_STACKOVERFLOW
select HAVE_CC_STACKPROTECTOR
+ select CPU_PM if CPU_IDLE
menu "Machine selection"
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 277dab3..97540a8 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -107,6 +107,8 @@ obj-$(CONFIG_JUMP_LABEL) += jump_label.o
obj-$(CONFIG_MIPS_CM) += mips-cm.o
obj-$(CONFIG_MIPS_CPC) += mips-cpc.o
+obj-$(CONFIG_CPU_PM) += pm.o
+
#
# DSP ASE supported for MIPS32 or MIPS64 Release 2 cores only. It is not
# safe to unconditionnaly use the assembler -mdsp / -mdspr2 switches
diff --git a/arch/mips/kernel/pm.c b/arch/mips/kernel/pm.c
new file mode 100644
index 0000000..112903f
--- /dev/null
+++ b/arch/mips/kernel/pm.c
@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2014 Imagination Technologies Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * CPU PM notifiers for saving/restoring general CPU state.
+ */
+
+#include <linux/cpu_pm.h>
+#include <linux/init.h>
+
+#include <asm/dsp.h>
+#include <asm/fpu.h>
+#include <asm/mmu_context.h>
+#include <asm/watch.h>
+
+/**
+ * mips_cpu_save() - Save general CPU state.
+ * Ensures that general CPU context is saved, notably FPU and DSP.
+ */
+static int mips_cpu_save(void)
+{
+ /* Save FPU state */
+ lose_fpu(1);
+
+ /* Save DSP state */
+ save_dsp(current);
+
+ return 0;
+}
+
+/**
+ * mips_cpu_restore() - Restore general CPU state.
+ * Restores important CPU context.
+ */
+static void mips_cpu_restore(void)
+{
+ unsigned int cpu = smp_processor_id();
+
+ /* Restore ASID */
+ if (current->mm)
+ write_c0_entryhi(cpu_asid(cpu, current->mm));
+
+ /* Restore DSP state */
+ restore_dsp(current);
+
+ /* Restore UserLocal */
+ if (cpu_has_userlocal)
+ write_c0_userlocal(current_thread_info()->tp_value);
+
+ /* Restore watch registers */
+ __restore_watch();
+}
+
+/**
+ * mips_pm_notifier() - Notifier for preserving general CPU context.
+ * @self: Notifier block.
+ * @cmd: CPU PM event.
+ * @v: Private data (unused).
+ *
+ * This is called when a CPU power management event occurs, and is used to
+ * ensure that important CPU context is preserved across a CPU power down.
+ */
+static int mips_pm_notifier(struct notifier_block *self, unsigned long cmd,
+ void *v)
+{
+ int ret;
+
+ switch (cmd) {
+ case CPU_PM_ENTER:
+ ret = mips_cpu_save();
+ if (ret)
+ return NOTIFY_STOP;
+ break;
+ case CPU_PM_ENTER_FAILED:
+ case CPU_PM_EXIT:
+ mips_cpu_restore();
+ break;
+ }
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block mips_pm_notifier_block = {
+ .notifier_call = mips_pm_notifier,
+};
+
+static int __init mips_pm_init(void)
+{
+ return cpu_pm_register_notifier(&mips_pm_notifier_block);
+}
+arch_initcall(mips_pm_init);
--
1.8.5.3
