On Wed, Sep 03 2014 at 11:46 -0600, Lorenzo Pieralisi wrote:

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

quoted

On Mon, Sep 01 2014 at 09:28 -0600, Lorenzo Pieralisi wrote:

quoted

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.

Ah, I was working on the premise that I may be using the same cpuidle
driver for ARM64. I guess I will worry about ARM64 with non-PSCI drivers
when and if I have to. Thanks!

Lorenzo

quoted

quoted

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Lorenzo Pieralisi <redacted>
---
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

--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo at vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html