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

[lorenzo.pieralisi@arm.com (Lorenzo Pieralisi)]

On Wed, Sep 03, 2014 at 06:34:37PM +0100, Lina Iyer wrote:
> 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?

I am not following you sorry. The ARM64 CPUidle driver calls the arm64
cpu_init_idle hooks to initialize idle states (in a generic way from
a driver perspective), not the other way around.

On ARM64 your idle driver rely on an arm64 suspend back-end (eg PSCI) to
enter idle states, it works in a different way from ARM, on purpose.

Have a look at what the code does, it won't be the same driver that's
for certain, since on arm64 I do not want to cope with per-platform
CPUidle state enter functions anymore, the arm64 cpu_ops suspend hook
implements the idle state enter method.

Lorenzo

> >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
> >
> >
> --
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