[PATCH v8 4/8] arm64: kernel: introduce cpu_init_idle CPU operation

[lina.iyer@linaro.org (Lina Iyer)]

On Mon, Sep 01 2014 at 09:28 -0600, Lorenzo Pieralisi wrote:
>The CPUidle subsystem on ARM64 machines requires the idle states
>implementation back-end to initialize idle states parameter upon
>boot. This patch adds a hook in the CPU operations structure that
>should be initialized by the CPU operations back-end in order to
>provide a function that initializes cpu idle states.
>
>This patch also adds the infrastructure to arm64 kernel required
>to export the CPU operations based initialization interface, so
>that drivers (ie CPUidle) can use it when they are initialized
>at probe time.
>
I like the change for ARM64.
However, that raises a question, how do I have the same driver that
should get probed by a platform device (on 32 bit ARM) and getting called
from cpu_init_idle on ARM64?

>Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
>Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
>---
> arch/arm64/include/asm/cpu_ops.h |  3 +++
> arch/arm64/include/asm/cpuidle.h | 13 +++++++++++++
> arch/arm64/kernel/Makefile       |  1 +
> arch/arm64/kernel/cpuidle.c      | 31 +++++++++++++++++++++++++++++++
> 4 files changed, 48 insertions(+)
> create mode 100644 arch/arm64/include/asm/cpuidle.h
> create mode 100644 arch/arm64/kernel/cpuidle.c
>
>diff --git a/arch/arm64/include/asm/cpu_ops.h b/arch/arm64/include/asm/cpu_ops.h
>index d7b4b38..47dfa31 100644
>--- a/arch/arm64/include/asm/cpu_ops.h
>+++ b/arch/arm64/include/asm/cpu_ops.h
>@@ -28,6 +28,8 @@ struct device_node;
>  *		enable-method property.
>  * @cpu_init:	Reads any data necessary for a specific enable-method from the
>  *		devicetree, for a given cpu node and proposed logical id.
>+ * @cpu_init_idle: Reads any data necessary to initialize CPU idle states from
>+ *		devicetree, for a given cpu node and proposed logical id.
>  * @cpu_prepare: Early one-time preparation step for a cpu. If there is a
>  *		mechanism for doing so, tests whether it is possible to boot
>  *		the given CPU.
>@@ -47,6 +49,7 @@ struct device_node;
> struct cpu_operations {
> 	const char	*name;
> 	int		(*cpu_init)(struct device_node *, unsigned int);
>+	int		(*cpu_init_idle)(struct device_node *, unsigned int);
> 	int		(*cpu_prepare)(unsigned int);
> 	int		(*cpu_boot)(unsigned int);
> 	void		(*cpu_postboot)(void);
>diff --git a/arch/arm64/include/asm/cpuidle.h b/arch/arm64/include/asm/cpuidle.h
>new file mode 100644
>index 0000000..b52a993
>--- /dev/null
>+++ b/arch/arm64/include/asm/cpuidle.h
>@@ -0,0 +1,13 @@
>+#ifndef __ASM_CPUIDLE_H
>+#define __ASM_CPUIDLE_H
>+
>+#ifdef CONFIG_CPU_IDLE
>+extern int cpu_init_idle(unsigned int cpu);
>+#else
>+static inline int cpu_init_idle(unsigned int cpu)
>+{
>+	return -EOPNOTSUPP;
>+}
>+#endif
>+
>+#endif
>diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
>index 383d81d..be78980 100644
>--- a/arch/arm64/kernel/Makefile
>+++ b/arch/arm64/kernel/Makefile
>@@ -27,6 +27,7 @@ arm64-obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o
> arm64-obj-$(CONFIG_HW_PERF_EVENTS)	+= perf_event.o
> arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
> arm64-obj-$(CONFIG_ARM64_CPU_SUSPEND)	+= sleep.o suspend.o
>+arm64-obj-$(CONFIG_CPU_IDLE)		+= cpuidle.o
> arm64-obj-$(CONFIG_JUMP_LABEL)		+= jump_label.o
> arm64-obj-$(CONFIG_KGDB)		+= kgdb.o
> arm64-obj-$(CONFIG_EFI)			+= efi.o efi-stub.o efi-entry.o
>diff --git a/arch/arm64/kernel/cpuidle.c b/arch/arm64/kernel/cpuidle.c
>new file mode 100644
>index 0000000..19d17f5
>--- /dev/null
>+++ b/arch/arm64/kernel/cpuidle.c
>@@ -0,0 +1,31 @@
>+/*
>+ * ARM64 CPU idle arch support
>+ *
>+ * Copyright (C) 2014 ARM Ltd.
>+ * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
>+ *
>+ * 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/of.h>
>+#include <linux/of_device.h>
>+
>+#include <asm/cpuidle.h>
>+#include <asm/cpu_ops.h>
>+
>+int cpu_init_idle(unsigned int cpu)
>+{
>+	int ret = -EOPNOTSUPP;
>+	struct device_node *cpu_node = of_cpu_device_node_get(cpu);
>+
>+	if (!cpu_node)
>+		return -ENODEV;
>+
>+	if (cpu_ops[cpu] && cpu_ops[cpu]->cpu_init_idle)
>+		ret = cpu_ops[cpu]->cpu_init_idle(cpu_node, cpu);
>+
>+	of_node_put(cpu_node);
>+	return ret;
>+}
>-- 
>1.9.1
>
>