Re: [PATCH v2 6/9] arm, arm64: factorize common cpu capacity default code

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Feb 09, 2017 at 09:25:22AM +0000, 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>
> ---
> 
> Changes from v1:
>  - keep the original GPLv2 header
> ---
>  arch/arm/Kconfig             |   1 +
>  arch/arm/kernel/topology.c   | 213 ++------------------------------------
>  arch/arm64/Kconfig           |   1 +
>  arch/arm64/kernel/topology.c | 219 +--------------------------------------
>  drivers/base/Kconfig         |   8 ++
>  drivers/base/Makefile        |   1 +
>  drivers/base/arch_topology.c | 237 +++++++++++++++++++++++++++++++++++++++++++
>  7 files changed, 257 insertions(+), 423 deletions(-)
>  create mode 100644 drivers/base/arch_topology.c

Ah, so you want _me_ to maintain this, ok, I better review it...

> --- 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.

Mix of spaces and tabs :(

> +
>  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..c1dd430adad2
> --- /dev/null
> +++ b/drivers/base/arch_topology.c
> @@ -0,0 +1,237 @@
> +/*
> + * driver/base/arch_topology.c - Arch specific cpu topology information

No need to keep the filename in the file, you know what it is called :)

> + *
> + * Copyright (C) 2016, ARM Ltd.
> + * Written by: Juri Lelli, ARM Ltd.
> + *
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License.  See the file "COPYING" in the main directory of this archive
> + * for more details.

So, v2 only?  Please be specific.  Even better yet, use a SPDX header if
you want to, those are always nice.

> + */
> +
> +#include <linux/acpi.h>
> +#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)

Why do you have sd here?  You never use it:

> +{
> +	return per_cpu(cpu_scale, cpu);

See?  What am I missing?

> +}
> +
> +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;

new line for:
	int i;
please.

> +	unsigned long new_capacity;
> +	ssize_t ret;
> +
> +	if (count) {

	if (!count)
		return 0;

then you can get on with the rest of the logic.  Don't indent if you
don't have to.

> +		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;
> +}

No documentation for these sysfs file?  Not good :(

> +
> +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);

What is this going to help with?

> +			continue;
> +		}
> +		device_create_file(cpu, &dev_attr_cpu_capacity);

You realize you just raced userspace, right?  Why do it this way and not
register the files when the CPU device is created/removed?

> +	}
> +
> +	return 0;
> +}
> +subsys_initcall(register_cpu_capacity_sysctl);
> +
> +u32 capacity_scale;
> +u32 *raw_capacity;
> +bool cap_parsing_failed;

globals?  really?  That's bold :(

> +
> +void normalize_cpu_capacity(void)

naming is hard, but try to put a good, descriptive, prefix on everything
you are exporting in the same file, the same prefix.

cpu_capacity_normalize()?
cpu_capacity_register_sysctl()?

and so on.

> +{
> +	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)

cpu_capacity_parse()?

thanks,

greg k-h