diff mbox

[RFC,8/8] arm64: add sysfs cpu_capacity attribute

Message ID 1448288921-30307-9-git-send-email-juri.lelli@arm.com
State Superseded
Headers show

Commit Message

Juri Lelli Nov. 23, 2015, 2:28 p.m. UTC 
Add a sysfs cpu_capacity attribute with which it is possible to read and
write (thus over-writing default values) CPUs capacity. This might be
useful in situation where there is no way to get proper default values
at boot time.

The new attribute shows up as:

 /sys/devices/system/cpu/cpu*/cpu_capacity

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Brown <broonie@linaro.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>

---
 arch/arm64/kernel/topology.c | 68 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

-- 
2.2.2

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Comments

Dietmar Eggemann Dec. 10, 2015, 2:15 p.m. UTC | #1 
On 23/11/15 14:28, Juri Lelli wrote:
> Add a sysfs cpu_capacity attribute with which it is possible to read and

> write (thus over-writing default values) CPUs capacity. This might be

> useful in situation where there is no way to get proper default values

> at boot time.

> 

> The new attribute shows up as:

> 

>  /sys/devices/system/cpu/cpu*/cpu_capacity

>


This sysfs interface is not really needed for arm or arm64. People can
build the dt blob if they want to change the values. Less code to carry
... Let's focus on the core functionality, which is parsing cpu capacity
from dt file to task scheduler for heterogeneous systems.

[...]

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diff mbox

Patch

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 4423cc5..5c9e477 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -35,6 +35,74 @@  static void set_capacity_scale(unsigned int cpu, unsigned long capacity)
 	per_cpu(cpu_scale, cpu) = capacity;
 }
 
+#ifdef CONFIG_PROC_SYSCTL
+#include <asm/cpu.h>
+#include <linux/string.h>
+static ssize_t show_cpu_capacity(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	struct cpu *cpu = container_of(dev, struct cpu, dev);
+	ssize_t rc;
+	int cpunum = cpu->dev.id;
+	unsigned long capacity = arch_scale_cpu_capacity(NULL, cpunum);
+
+	rc = sprintf(buf, "%lu\n", capacity);
+
+	return rc;
+}
+
+static ssize_t store_cpu_capacity(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) {
+		char *p = (char *) buf;
+
+		ret = kstrtoul(p, 0, &new_capacity);
+		if (ret)
+			return ret;
+		if (new_capacity > SCHED_CAPACITY_SCALE)
+			return -EINVAL;
+
+		for_each_cpu(i, &cpu_topology[this_cpu].core_sibling)
+			set_capacity_scale(i, new_capacity);
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR(cpu_capacity,
+		   0644,
+		   show_cpu_capacity,
+		   store_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;
+}
+late_initcall(register_cpu_capacity_sysctl);
+#endif
+
 static u32 capacity_scale = SCHED_CAPACITY_SCALE;
 
 static void __init parse_cpu_capacity(struct device_node *cpu_node, int cpu)