diff mbox

[6/7] arm, arm64: factorize common cpu capacity default code

Message ID 20170119143757.14537-7-juri.lelli@arm.com (mailing list archive)
State Not Applicable, archived
Headers show

Commit Message

Juri Lelli Jan. 19, 2017, 2:37 p.m. UTC
arm and arm64 share lot of code relative to parsing CPU capacity
information from DT, using that information for appropriate scaling and
exposing a sysfs interface for chaging such values at runtime.

Factorize such code in a common place (driver/base/arch_topology.c) in
preparation for further additions.

Suggested-by: Will Deacon <will.deacon@arm.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
---
 arch/arm/Kconfig             |   1 +
 arch/arm/kernel/topology.c   | 213 ++------------------------------------
 arch/arm64/Kconfig           |   1 +
 arch/arm64/kernel/topology.c | 213 +-------------------------------------
 drivers/base/Kconfig         |   8 ++
 drivers/base/Makefile        |   1 +
 drivers/base/arch_topology.c | 240 +++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 260 insertions(+), 417 deletions(-)
 create mode 100644 drivers/base/arch_topology.c

Comments

Russell King (Oracle) Jan. 19, 2017, 2:53 p.m. UTC | #1
On Thu, Jan 19, 2017 at 02:37:56PM +0000, Juri Lelli wrote:
> +extern unsigned long
> +arch_scale_cpu_capacity(struct sched_domain *sd, int cpu);
> +extern void set_capacity_scale(unsigned int cpu, unsigned long capacity);

These should be in a header file (please run your code through sparse).

> +extern bool cap_parsing_failed;
> +extern void normalize_cpu_capacity(void);
> +extern int __init parse_cpu_capacity(struct device_node *cpu_node, int cpu);

Same for these.

> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> new file mode 100644
> index 000000000000..3faf89518892
> --- /dev/null
> +++ b/drivers/base/arch_topology.c
> @@ -0,0 +1,240 @@
> +/*
> + * driver/base/arch_topology.c - Arch specific cpu topology information
> + *
> + * Written by: Juri Lelli, ARM Ltd.
> + *
> + * Copyright (C) 2016, ARM Ltd.
> + *
> + * All rights reserved.
> + *
> + * 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.

The files that you've taken this code from are GPLv2, but you've thrown
a GPLv2+ header on a file that's merely a copy of the original code.
As some of the code you've moved to this new file is from Nicolas and
Vincent, you need to seek their approval to make this change of license
terms, or keep the original license terms.
Juri Lelli Jan. 19, 2017, 3:51 p.m. UTC | #2
Hi,

On 19/01/17 14:53, Russell King - ARM Linux wrote:
> On Thu, Jan 19, 2017 at 02:37:56PM +0000, Juri Lelli wrote:
> > +extern unsigned long
> > +arch_scale_cpu_capacity(struct sched_domain *sd, int cpu);
> > +extern void set_capacity_scale(unsigned int cpu, unsigned long capacity);
> 
> These should be in a header file (please run your code through sparse).
> 
> > +extern bool cap_parsing_failed;
> > +extern void normalize_cpu_capacity(void);
> > +extern int __init parse_cpu_capacity(struct device_node *cpu_node, int cpu);
> 
> Same for these.
> 

Right, I was wondering where to put these in the cover letter. New
header file (e.g., include/linux/arch_topology.h) or some existing one? 

> > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> > new file mode 100644
> > index 000000000000..3faf89518892
> > --- /dev/null
> > +++ b/drivers/base/arch_topology.c
> > @@ -0,0 +1,240 @@
> > +/*
> > + * driver/base/arch_topology.c - Arch specific cpu topology information
> > + *
> > + * Written by: Juri Lelli, ARM Ltd.
> > + *
> > + * Copyright (C) 2016, ARM Ltd.
> > + *
> > + * All rights reserved.
> > + *
> > + * 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.
> 
> The files that you've taken this code from are GPLv2, but you've thrown
> a GPLv2+ header on a file that's merely a copy of the original code.
> As some of the code you've moved to this new file is from Nicolas and
> Vincent, you need to seek their approval to make this change of license
> terms, or keep the original license terms.
> 

Apologies. I'd say we keep the original one. I'll modify it in the next
version.

Thanks,

- Juri
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Dietmar Eggemann Jan. 19, 2017, 4 p.m. UTC | #3
On 19/01/17 14:37, Juri Lelli wrote:
> arm and arm64 share lot of code relative to parsing CPU capacity
> information from DT, using that information for appropriate scaling and
> exposing a sysfs interface for chaging such values at runtime.
> 
> Factorize such code in a common place (driver/base/arch_topology.c) in
> preparation for further additions.
> 
> Suggested-by: Will Deacon <will.deacon@arm.com>
> Suggested-by: Mark Rutland <mark.rutland@arm.com>
> Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Juri Lelli <juri.lelli@arm.com>
> ---
>  arch/arm/Kconfig             |   1 +
>  arch/arm/kernel/topology.c   | 213 ++------------------------------------
>  arch/arm64/Kconfig           |   1 +
>  arch/arm64/kernel/topology.c | 213 +-------------------------------------
>  drivers/base/Kconfig         |   8 ++
>  drivers/base/Makefile        |   1 +
>  drivers/base/arch_topology.c | 240 +++++++++++++++++++++++++++++++++++++++++++
>  7 files changed, 260 insertions(+), 417 deletions(-)
>  create mode 100644 drivers/base/arch_topology.c

[...]

> +extern unsigned long
> +arch_scale_cpu_capacity(struct sched_domain *sd, int cpu);

How about adding a driver specific prefix 'foo_' to all driver interfaces?

I'm asking because I would rather like to do a

#define arch_scale_cpu_capacity foo_scale_cpu_capacity

then a

#define arch_scale_cpu_capacity arch_scale_cpu_capacity

in arch/arm64/include/asm/topology.h

later to wire cpu-invariant load-tracking support up to the task
scheduler for ARM64.

That's probably true too for all the 'driver' interfaces which get used
in arch/arm{,64}/kernel/topology.c.

[...]


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Juri Lelli Jan. 20, 2017, 10:42 a.m. UTC | #4
Hi Dietmar,

On 19/01/17 16:00, Dietmar Eggemann wrote:
> On 19/01/17 14:37, Juri Lelli wrote:
> > arm and arm64 share lot of code relative to parsing CPU capacity
> > information from DT, using that information for appropriate scaling and
> > exposing a sysfs interface for chaging such values at runtime.
> > 
> > Factorize such code in a common place (driver/base/arch_topology.c) in
> > preparation for further additions.
> > 
> > Suggested-by: Will Deacon <will.deacon@arm.com>
> > Suggested-by: Mark Rutland <mark.rutland@arm.com>
> > Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Russell King <linux@armlinux.org.uk>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Will Deacon <will.deacon@arm.com>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Signed-off-by: Juri Lelli <juri.lelli@arm.com>
> > ---
> >  arch/arm/Kconfig             |   1 +
> >  arch/arm/kernel/topology.c   | 213 ++------------------------------------
> >  arch/arm64/Kconfig           |   1 +
> >  arch/arm64/kernel/topology.c | 213 +-------------------------------------
> >  drivers/base/Kconfig         |   8 ++
> >  drivers/base/Makefile        |   1 +
> >  drivers/base/arch_topology.c | 240 +++++++++++++++++++++++++++++++++++++++++++
> >  7 files changed, 260 insertions(+), 417 deletions(-)
> >  create mode 100644 drivers/base/arch_topology.c
> 
> [...]
> 
> > +extern unsigned long
> > +arch_scale_cpu_capacity(struct sched_domain *sd, int cpu);
> 
> How about adding a driver specific prefix 'foo_' to all driver interfaces?
> 
> I'm asking because I would rather like to do a
> 
> #define arch_scale_cpu_capacity foo_scale_cpu_capacity
> 
> then a
> 
> #define arch_scale_cpu_capacity arch_scale_cpu_capacity
> 
> in arch/arm64/include/asm/topology.h
> 
> later to wire cpu-invariant load-tracking support up to the task
> scheduler for ARM64.
> 
> That's probably true too for all the 'driver' interfaces which get used
> in arch/arm{,64}/kernel/topology.c.
> 

Looks like a good way to improve clarity to me. I'll add a patch for the
next version doing this and we see what people think.

Best,

- Juri
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diff mbox

Patch

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 186c4c214e0a..f7059b3a1265 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -19,6 +19,7 @@  config ARM
 	select EDAC_SUPPORT
 	select EDAC_ATOMIC_SCRUB
 	select GENERIC_ALLOCATOR
+	select GENERIC_ARCH_TOPOLOGY
 	select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI)
 	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
 	select GENERIC_EARLY_IOREMAP
diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index c760a321935b..51e9ed6439f1 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -43,75 +43,10 @@ 
  * to run the rebalance_domains for all idle cores and the cpu_capacity can be
  * updated during this sequence.
  */
-static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
-static DEFINE_MUTEX(cpu_scale_mutex);
 
-unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
-{
-	return per_cpu(cpu_scale, cpu);
-}
-
-static void set_capacity_scale(unsigned int cpu, unsigned long capacity)
-{
-	per_cpu(cpu_scale, cpu) = capacity;
-}
-
-static ssize_t cpu_capacity_show(struct device *dev,
-				 struct device_attribute *attr,
-				 char *buf)
-{
-	struct cpu *cpu = container_of(dev, struct cpu, dev);
-
-	return sprintf(buf, "%lu\n",
-			arch_scale_cpu_capacity(NULL, cpu->dev.id));
-}
-
-static ssize_t cpu_capacity_store(struct device *dev,
-				  struct device_attribute *attr,
-				  const char *buf,
-				  size_t count)
-{
-	struct cpu *cpu = container_of(dev, struct cpu, dev);
-	int this_cpu = cpu->dev.id, i;
-	unsigned long new_capacity;
-	ssize_t ret;
-
-	if (count) {
-		ret = kstrtoul(buf, 0, &new_capacity);
-		if (ret)
-			return ret;
-		if (new_capacity > SCHED_CAPACITY_SCALE)
-			return -EINVAL;
-
-		mutex_lock(&cpu_scale_mutex);
-		for_each_cpu(i, &cpu_topology[this_cpu].core_sibling)
-			set_capacity_scale(i, new_capacity);
-		mutex_unlock(&cpu_scale_mutex);
-	}
-
-	return count;
-}
-
-static DEVICE_ATTR_RW(cpu_capacity);
-
-static int register_cpu_capacity_sysctl(void)
-{
-	int i;
-	struct device *cpu;
-
-	for_each_possible_cpu(i) {
-		cpu = get_cpu_device(i);
-		if (!cpu) {
-			pr_err("%s: too early to get CPU%d device!\n",
-			       __func__, i);
-			continue;
-		}
-		device_create_file(cpu, &dev_attr_cpu_capacity);
-	}
-
-	return 0;
-}
-subsys_initcall(register_cpu_capacity_sysctl);
+extern unsigned long
+arch_scale_cpu_capacity(struct sched_domain *sd, int cpu);
+extern void set_capacity_scale(unsigned int cpu, unsigned long capacity);
 
 #ifdef CONFIG_OF
 struct cpu_efficiency {
@@ -140,145 +75,9 @@  static unsigned long *__cpu_capacity;
 
 static unsigned long middle_capacity = 1;
 static bool cap_from_dt = true;
-static u32 *raw_capacity;
-static bool cap_parsing_failed;
-static u32 capacity_scale;
-
-static int __init parse_cpu_capacity(struct device_node *cpu_node, int cpu)
-{
-	int ret = 1;
-	u32 cpu_capacity;
-
-	if (cap_parsing_failed)
-		return !ret;
-
-	ret = of_property_read_u32(cpu_node,
-				   "capacity-dmips-mhz",
-				   &cpu_capacity);
-	if (!ret) {
-		if (!raw_capacity) {
-			raw_capacity = kcalloc(num_possible_cpus(),
-					       sizeof(*raw_capacity),
-					       GFP_KERNEL);
-			if (!raw_capacity) {
-				pr_err("cpu_capacity: failed to allocate memory for raw capacities\n");
-				cap_parsing_failed = true;
-				return ret;
-			}
-		}
-		capacity_scale = max(cpu_capacity, capacity_scale);
-		raw_capacity[cpu] = cpu_capacity;
-		pr_debug("cpu_capacity: %s cpu_capacity=%u (raw)\n",
-			cpu_node->full_name, raw_capacity[cpu]);
-	} else {
-		if (raw_capacity) {
-			pr_err("cpu_capacity: missing %s raw capacity\n",
-				cpu_node->full_name);
-			pr_err("cpu_capacity: partial information: fallback to 1024 for all CPUs\n");
-		}
-		cap_parsing_failed = true;
-		kfree(raw_capacity);
-	}
-
-	return !ret;
-}
-
-static void normalize_cpu_capacity(void)
-{
-	u64 capacity;
-	int cpu;
-
-	if (!raw_capacity || cap_parsing_failed)
-		return;
-
-	pr_debug("cpu_capacity: capacity_scale=%u\n", capacity_scale);
-	mutex_lock(&cpu_scale_mutex);
-	for_each_possible_cpu(cpu) {
-		capacity = (raw_capacity[cpu] << SCHED_CAPACITY_SHIFT)
-			/ capacity_scale;
-		set_capacity_scale(cpu, capacity);
-		pr_debug("cpu_capacity: CPU%d cpu_capacity=%lu\n",
-			cpu, arch_scale_cpu_capacity(NULL, cpu));
-	}
-	mutex_unlock(&cpu_scale_mutex);
-}
-
-#ifdef CONFIG_CPU_FREQ
-static cpumask_var_t cpus_to_visit;
-static bool cap_parsing_done;
-static void parsing_done_workfn(struct work_struct *work);
-static DECLARE_WORK(parsing_done_work, parsing_done_workfn);
-
-static int
-init_cpu_capacity_callback(struct notifier_block *nb,
-			   unsigned long val,
-			   void *data)
-{
-	struct cpufreq_policy *policy = data;
-	int cpu;
-
-	if (cap_parsing_failed || cap_parsing_done)
-		return 0;
-
-	switch (val) {
-	case CPUFREQ_NOTIFY:
-		pr_debug("cpu_capacity: init cpu capacity for CPUs [%*pbl] (to_visit=%*pbl)\n",
-				cpumask_pr_args(policy->related_cpus),
-				cpumask_pr_args(cpus_to_visit));
-		cpumask_andnot(cpus_to_visit,
-			       cpus_to_visit,
-			       policy->related_cpus);
-		for_each_cpu(cpu, policy->related_cpus) {
-			raw_capacity[cpu] = arch_scale_cpu_capacity(NULL, cpu) *
-					    policy->cpuinfo.max_freq / 1000UL;
-			capacity_scale = max(raw_capacity[cpu], capacity_scale);
-		}
-		if (cpumask_empty(cpus_to_visit)) {
-			normalize_cpu_capacity();
-			kfree(raw_capacity);
-			pr_debug("cpu_capacity: parsing done\n");
-			cap_parsing_done = true;
-			schedule_work(&parsing_done_work);
-		}
-	}
-	return 0;
-}
-
-static struct notifier_block init_cpu_capacity_notifier = {
-	.notifier_call = init_cpu_capacity_callback,
-};
-
-static int __init register_cpufreq_notifier(void)
-{
-	if (cap_parsing_failed)
-		return -EINVAL;
-
-	if (!alloc_cpumask_var(&cpus_to_visit, GFP_KERNEL)) {
-		pr_err("cpu_capacity: failed to allocate memory for cpus_to_visit\n");
-		return -ENOMEM;
-	}
-	cpumask_copy(cpus_to_visit, cpu_possible_mask);
-
-	return cpufreq_register_notifier(&init_cpu_capacity_notifier,
-					 CPUFREQ_POLICY_NOTIFIER);
-}
-core_initcall(register_cpufreq_notifier);
-
-static void parsing_done_workfn(struct work_struct *work)
-{
-	cpufreq_unregister_notifier(&init_cpu_capacity_notifier,
-					 CPUFREQ_POLICY_NOTIFIER);
-}
-
-#else
-static int __init free_raw_capacity(void)
-{
-	kfree(raw_capacity);
-
-	return 0;
-}
-core_initcall(free_raw_capacity);
-#endif
+extern bool cap_parsing_failed;
+extern void normalize_cpu_capacity(void);
+extern int __init parse_cpu_capacity(struct device_node *cpu_node, int cpu);
 
 /*
  * Iterate all CPUs' descriptor in DT and compute the efficiency
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 111742126897..7534bb41ee09 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -36,6 +36,7 @@  config ARM64
 	select EDAC_SUPPORT
 	select FRAME_POINTER
 	select GENERIC_ALLOCATOR
+	select GENERIC_ARCH_TOPOLOGY
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_CLOCKEVENTS_BROADCAST
 	select GENERIC_CPU_AUTOPROBE
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 62b370388d72..f629f7524d65 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -21,221 +21,14 @@ 
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/string.h>
-#include <linux/cpufreq.h>
 
 #include <asm/cpu.h>
 #include <asm/cputype.h>
 #include <asm/topology.h>
 
-static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
-static DEFINE_MUTEX(cpu_scale_mutex);
-
-unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
-{
-	return per_cpu(cpu_scale, cpu);
-}
-
-static void set_capacity_scale(unsigned int cpu, unsigned long capacity)
-{
-	per_cpu(cpu_scale, cpu) = capacity;
-}
-
-static ssize_t cpu_capacity_show(struct device *dev,
-				 struct device_attribute *attr,
-				 char *buf)
-{
-	struct cpu *cpu = container_of(dev, struct cpu, dev);
-
-	return sprintf(buf, "%lu\n",
-			arch_scale_cpu_capacity(NULL, cpu->dev.id));
-}
-
-static ssize_t cpu_capacity_store(struct device *dev,
-				  struct device_attribute *attr,
-				  const char *buf,
-				  size_t count)
-{
-	struct cpu *cpu = container_of(dev, struct cpu, dev);
-	int this_cpu = cpu->dev.id, i;
-	unsigned long new_capacity;
-	ssize_t ret;
-
-	if (count) {
-		ret = kstrtoul(buf, 0, &new_capacity);
-		if (ret)
-			return ret;
-		if (new_capacity > SCHED_CAPACITY_SCALE)
-			return -EINVAL;
-
-		mutex_lock(&cpu_scale_mutex);
-		for_each_cpu(i, &cpu_topology[this_cpu].core_sibling)
-			set_capacity_scale(i, new_capacity);
-		mutex_unlock(&cpu_scale_mutex);
-	}
-
-	return count;
-}
-
-static DEVICE_ATTR_RW(cpu_capacity);
-
-static int register_cpu_capacity_sysctl(void)
-{
-	int i;
-	struct device *cpu;
-
-	for_each_possible_cpu(i) {
-		cpu = get_cpu_device(i);
-		if (!cpu) {
-			pr_err("%s: too early to get CPU%d device!\n",
-			       __func__, i);
-			continue;
-		}
-		device_create_file(cpu, &dev_attr_cpu_capacity);
-	}
-
-	return 0;
-}
-subsys_initcall(register_cpu_capacity_sysctl);
-
-static u32 capacity_scale;
-static u32 *raw_capacity;
-static bool cap_parsing_failed;
-
-static void __init parse_cpu_capacity(struct device_node *cpu_node, int cpu)
-{
-	int ret;
-	u32 cpu_capacity;
-
-	if (cap_parsing_failed)
-		return;
-
-	ret = of_property_read_u32(cpu_node,
-				   "capacity-dmips-mhz",
-				   &cpu_capacity);
-	if (!ret) {
-		if (!raw_capacity) {
-			raw_capacity = kcalloc(num_possible_cpus(),
-					       sizeof(*raw_capacity),
-					       GFP_KERNEL);
-			if (!raw_capacity) {
-				pr_err("cpu_capacity: failed to allocate memory for raw capacities\n");
-				cap_parsing_failed = true;
-				return;
-			}
-		}
-		capacity_scale = max(cpu_capacity, capacity_scale);
-		raw_capacity[cpu] = cpu_capacity;
-		pr_debug("cpu_capacity: %s cpu_capacity=%u (raw)\n",
-			cpu_node->full_name, raw_capacity[cpu]);
-	} else {
-		if (raw_capacity) {
-			pr_err("cpu_capacity: missing %s raw capacity\n",
-				cpu_node->full_name);
-			pr_err("cpu_capacity: partial information: fallback to 1024 for all CPUs\n");
-		}
-		cap_parsing_failed = true;
-		kfree(raw_capacity);
-	}
-}
-
-static void normalize_cpu_capacity(void)
-{
-	u64 capacity;
-	int cpu;
-
-	if (!raw_capacity || cap_parsing_failed)
-		return;
-
-	pr_debug("cpu_capacity: capacity_scale=%u\n", capacity_scale);
-	mutex_lock(&cpu_scale_mutex);
-	for_each_possible_cpu(cpu) {
-		pr_debug("cpu_capacity: cpu=%d raw_capacity=%u\n",
-			 cpu, raw_capacity[cpu]);
-		capacity = (raw_capacity[cpu] << SCHED_CAPACITY_SHIFT)
-			/ capacity_scale;
-		set_capacity_scale(cpu, capacity);
-		pr_debug("cpu_capacity: CPU%d cpu_capacity=%lu\n",
-			cpu, arch_scale_cpu_capacity(NULL, cpu));
-	}
-	mutex_unlock(&cpu_scale_mutex);
-}
-
-#ifdef CONFIG_CPU_FREQ
-static cpumask_var_t cpus_to_visit;
-static bool cap_parsing_done;
-static void parsing_done_workfn(struct work_struct *work);
-static DECLARE_WORK(parsing_done_work, parsing_done_workfn);
-
-static int
-init_cpu_capacity_callback(struct notifier_block *nb,
-			   unsigned long val,
-			   void *data)
-{
-	struct cpufreq_policy *policy = data;
-	int cpu;
-
-	if (cap_parsing_failed || cap_parsing_done)
-		return 0;
-
-	switch (val) {
-	case CPUFREQ_NOTIFY:
-		pr_debug("cpu_capacity: init cpu capacity for CPUs [%*pbl] (to_visit=%*pbl)\n",
-				cpumask_pr_args(policy->related_cpus),
-				cpumask_pr_args(cpus_to_visit));
-		cpumask_andnot(cpus_to_visit,
-			       cpus_to_visit,
-			       policy->related_cpus);
-		for_each_cpu(cpu, policy->related_cpus) {
-			raw_capacity[cpu] = arch_scale_cpu_capacity(NULL, cpu) *
-					    policy->cpuinfo.max_freq / 1000UL;
-			capacity_scale = max(raw_capacity[cpu], capacity_scale);
-		}
-		if (cpumask_empty(cpus_to_visit)) {
-			normalize_cpu_capacity();
-			kfree(raw_capacity);
-			pr_debug("cpu_capacity: parsing done\n");
-			cap_parsing_done = true;
-			schedule_work(&parsing_done_work);
-		}
-	}
-	return 0;
-}
-
-static struct notifier_block init_cpu_capacity_notifier = {
-	.notifier_call = init_cpu_capacity_callback,
-};
-
-static int __init register_cpufreq_notifier(void)
-{
-	if (cap_parsing_failed)
-		return -EINVAL;
-
-	if (!alloc_cpumask_var(&cpus_to_visit, GFP_KERNEL)) {
-		pr_err("cpu_capacity: failed to allocate memory for cpus_to_visit\n");
-		return -ENOMEM;
-	}
-	cpumask_copy(cpus_to_visit, cpu_possible_mask);
-
-	return cpufreq_register_notifier(&init_cpu_capacity_notifier,
-					 CPUFREQ_POLICY_NOTIFIER);
-}
-core_initcall(register_cpufreq_notifier);
-
-static void parsing_done_workfn(struct work_struct *work)
-{
-	cpufreq_unregister_notifier(&init_cpu_capacity_notifier,
-					 CPUFREQ_POLICY_NOTIFIER);
-}
-
-#else
-static int __init free_raw_capacity(void)
-{
-	kfree(raw_capacity);
-
-	return 0;
-}
-core_initcall(free_raw_capacity);
-#endif
+extern bool cap_parsing_failed;
+extern void normalize_cpu_capacity(void);
+extern int __init parse_cpu_capacity(struct device_node *cpu_node, int cpu);
 
 static int __init get_cpu_for_node(struct device_node *node)
 {
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index d718ae4b907a..307ea31187dd 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -339,4 +339,12 @@  config CMA_ALIGNMENT
 
 endif
 
+config GENERIC_ARCH_TOPOLOGY
+	bool
+	help
+	  Enable support for architectures common topology code: e.g., parsing
+	  CPU capacity information from DT, usage of such information for
+	  appropriate scaling, sysfs interface for changing capacity values at
+          runtime.
+
 endmenu
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index f2816f6ff76a..397e5c344e6a 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -23,6 +23,7 @@  obj-$(CONFIG_SOC_BUS) += soc.o
 obj-$(CONFIG_PINCTRL) += pinctrl.o
 obj-$(CONFIG_DEV_COREDUMP) += devcoredump.o
 obj-$(CONFIG_GENERIC_MSI_IRQ_DOMAIN) += platform-msi.o
+obj-$(CONFIG_GENERIC_ARCH_TOPOLOGY) += arch_topology.o
 
 obj-y			+= test/
 
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
new file mode 100644
index 000000000000..3faf89518892
--- /dev/null
+++ b/drivers/base/arch_topology.c
@@ -0,0 +1,240 @@ 
+/*
+ * driver/base/arch_topology.c - Arch specific cpu topology information
+ *
+ * Written by: Juri Lelli, ARM Ltd.
+ *
+ * Copyright (C) 2016, ARM Ltd.
+ *
+ * All rights reserved.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ */
+#include <linux/cpu.h>
+#include <linux/cpufreq.h>
+#include <linux/device.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/topology.h>
+
+static DEFINE_MUTEX(cpu_scale_mutex);
+static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
+
+unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
+{
+	return per_cpu(cpu_scale, cpu);
+}
+
+void set_capacity_scale(unsigned int cpu, unsigned long capacity)
+{
+	per_cpu(cpu_scale, cpu) = capacity;
+}
+
+static ssize_t cpu_capacity_show(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	struct cpu *cpu = container_of(dev, struct cpu, dev);
+
+	return sprintf(buf, "%lu\n",
+			arch_scale_cpu_capacity(NULL, cpu->dev.id));
+}
+
+static ssize_t cpu_capacity_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf,
+				  size_t count)
+{
+	struct cpu *cpu = container_of(dev, struct cpu, dev);
+	int this_cpu = cpu->dev.id, i;
+	unsigned long new_capacity;
+	ssize_t ret;
+
+	if (count) {
+		ret = kstrtoul(buf, 0, &new_capacity);
+		if (ret)
+			return ret;
+		if (new_capacity > SCHED_CAPACITY_SCALE)
+			return -EINVAL;
+
+		mutex_lock(&cpu_scale_mutex);
+		for_each_cpu(i, &cpu_topology[this_cpu].core_sibling)
+			set_capacity_scale(i, new_capacity);
+		mutex_unlock(&cpu_scale_mutex);
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(cpu_capacity);
+
+static int register_cpu_capacity_sysctl(void)
+{
+	int i;
+	struct device *cpu;
+
+	for_each_possible_cpu(i) {
+		cpu = get_cpu_device(i);
+		if (!cpu) {
+			pr_err("%s: too early to get CPU%d device!\n",
+			       __func__, i);
+			continue;
+		}
+		device_create_file(cpu, &dev_attr_cpu_capacity);
+	}
+
+	return 0;
+}
+subsys_initcall(register_cpu_capacity_sysctl);
+
+u32 capacity_scale;
+u32 *raw_capacity;
+bool cap_parsing_failed;
+
+void normalize_cpu_capacity(void)
+{
+	u64 capacity;
+	int cpu;
+
+	if (!raw_capacity || cap_parsing_failed)
+		return;
+
+	pr_debug("cpu_capacity: capacity_scale=%u\n", capacity_scale);
+	mutex_lock(&cpu_scale_mutex);
+	for_each_possible_cpu(cpu) {
+		pr_debug("cpu_capacity: cpu=%d raw_capacity=%u\n",
+			 cpu, raw_capacity[cpu]);
+		capacity = (raw_capacity[cpu] << SCHED_CAPACITY_SHIFT)
+			/ capacity_scale;
+		set_capacity_scale(cpu, capacity);
+		pr_debug("cpu_capacity: CPU%d cpu_capacity=%lu\n",
+			cpu, arch_scale_cpu_capacity(NULL, cpu));
+	}
+	mutex_unlock(&cpu_scale_mutex);
+}
+
+int __init parse_cpu_capacity(struct device_node *cpu_node, int cpu)
+{
+	int ret = 1;
+	u32 cpu_capacity;
+
+	if (cap_parsing_failed)
+		return !ret;
+
+	ret = of_property_read_u32(cpu_node,
+				   "capacity-dmips-mhz",
+				   &cpu_capacity);
+	if (!ret) {
+		if (!raw_capacity) {
+			raw_capacity = kcalloc(num_possible_cpus(),
+					       sizeof(*raw_capacity),
+					       GFP_KERNEL);
+			if (!raw_capacity) {
+				pr_err("cpu_capacity: failed to allocate memory for raw capacities\n");
+				cap_parsing_failed = true;
+				return ret;
+			}
+		}
+		capacity_scale = max(cpu_capacity, capacity_scale);
+		raw_capacity[cpu] = cpu_capacity;
+		pr_debug("cpu_capacity: %s cpu_capacity=%u (raw)\n",
+			cpu_node->full_name, raw_capacity[cpu]);
+	} else {
+		if (raw_capacity) {
+			pr_err("cpu_capacity: missing %s raw capacity\n",
+				cpu_node->full_name);
+			pr_err("cpu_capacity: partial information: fallback to 1024 for all CPUs\n");
+		}
+		cap_parsing_failed = true;
+		kfree(raw_capacity);
+	}
+
+	return !ret;
+}
+
+#ifdef CONFIG_CPU_FREQ
+static cpumask_var_t cpus_to_visit;
+static bool cap_parsing_done;
+static void parsing_done_workfn(struct work_struct *work);
+static DECLARE_WORK(parsing_done_work, parsing_done_workfn);
+
+static int
+init_cpu_capacity_callback(struct notifier_block *nb,
+			   unsigned long val,
+			   void *data)
+{
+	struct cpufreq_policy *policy = data;
+	int cpu;
+
+	if (cap_parsing_failed || cap_parsing_done)
+		return 0;
+
+	switch (val) {
+	case CPUFREQ_NOTIFY:
+		pr_debug("cpu_capacity: init cpu capacity for CPUs [%*pbl] (to_visit=%*pbl)\n",
+				cpumask_pr_args(policy->related_cpus),
+				cpumask_pr_args(cpus_to_visit));
+		cpumask_andnot(cpus_to_visit,
+			       cpus_to_visit,
+			       policy->related_cpus);
+		for_each_cpu(cpu, policy->related_cpus) {
+			raw_capacity[cpu] = arch_scale_cpu_capacity(NULL, cpu) *
+					    policy->cpuinfo.max_freq / 1000UL;
+			capacity_scale = max(raw_capacity[cpu], capacity_scale);
+		}
+		if (cpumask_empty(cpus_to_visit)) {
+			normalize_cpu_capacity();
+			kfree(raw_capacity);
+			pr_debug("cpu_capacity: parsing done\n");
+			cap_parsing_done = true;
+			schedule_work(&parsing_done_work);
+		}
+	}
+	return 0;
+}
+
+static struct notifier_block init_cpu_capacity_notifier = {
+	.notifier_call = init_cpu_capacity_callback,
+};
+
+static int __init register_cpufreq_notifier(void)
+{
+	if (cap_parsing_failed)
+		return -EINVAL;
+
+	if (!alloc_cpumask_var(&cpus_to_visit, GFP_KERNEL)) {
+		pr_err("cpu_capacity: failed to allocate memory for cpus_to_visit\n");
+		return -ENOMEM;
+	}
+	cpumask_copy(cpus_to_visit, cpu_possible_mask);
+
+	return cpufreq_register_notifier(&init_cpu_capacity_notifier,
+					 CPUFREQ_POLICY_NOTIFIER);
+}
+core_initcall(register_cpufreq_notifier);
+
+static void parsing_done_workfn(struct work_struct *work)
+{
+	cpufreq_unregister_notifier(&init_cpu_capacity_notifier,
+					 CPUFREQ_POLICY_NOTIFIER);
+}
+
+#else
+static int __init free_raw_capacity(void)
+{
+	kfree(raw_capacity);
+
+	return 0;
+}
+core_initcall(free_raw_capacity);
+#endif