diff mbox series

MIPS: Expose prid and globalnumber to sysfs

Message ID 20220809113444.17757-1-jiaxun.yang@flygoat.com (mailing list archive)
State Superseded
Headers show
Series MIPS: Expose prid and globalnumber to sysfs | expand

Commit Message

Jiaxun Yang Aug. 9, 2022, 11:34 a.m. UTC 
Some application would like to know precise model and rev of processor
to do errata workaround or optimization.

Expose them in sysfs as:
/sys/devices/system/cpu/cpuX/regs/identification/prid
/sys/devices/system/cpu/cpuX/regs/identification/globalnumber

Reusing AArch64 CPU registers directory.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
 .../ABI/testing/sysfs-devices-system-cpu      | 11 +++
 arch/mips/kernel/topology.c                   | 96 +++++++++++++++++++
 2 files changed, 107 insertions(+)

Comments

Greg KH Aug. 9, 2022, 12:08 p.m. UTC | #1 
On Tue, Aug 09, 2022 at 11:34:44AM +0000, Jiaxun Yang wrote:
> Some application would like to know precise model and rev of processor
> to do errata workaround or optimization.
> 
> Expose them in sysfs as:
> /sys/devices/system/cpu/cpuX/regs/identification/prid
> /sys/devices/system/cpu/cpuX/regs/identification/globalnumber
> 
> Reusing AArch64 CPU registers directory.
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
>  .../ABI/testing/sysfs-devices-system-cpu      | 11 +++
>  arch/mips/kernel/topology.c                   | 96 +++++++++++++++++++
>  2 files changed, 107 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
> index 5bf61881f012..adf855e7bb9b 100644
> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
> @@ -512,6 +512,17 @@ Description:	information about CPUs heterogeneity.
>  
>  		cpu_capacity: capacity of cpuX.
>  
> +What:		/sys/devices/system/cpu/cpuX/regs/
> +		/sys/devices/system/cpu/cpuX/regs/identification/
> +		/sys/devices/system/cpu/cpuX/regs/identification/prid
> +		/sys/devices/system/cpu/cpuX/regs/identification/globalnumber
> +Date:		Augest 2022
> +Contact:	Linux MIPS Kernel Mailing list <linux-mips@vger.kernel.org>
> +Description:	MIPS CPU registers
> +
> +		'identification' directory exposes the Processor ID and Global Number
> +		registers for identifying model and revision of the CPU.
> +
>  What:		/sys/devices/system/cpu/vulnerabilities
>  		/sys/devices/system/cpu/vulnerabilities/meltdown
>  		/sys/devices/system/cpu/vulnerabilities/spectre_v1
> diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c
> index 9429d85a4703..90b5136afb63 100644
> --- a/arch/mips/kernel/topology.c
> +++ b/arch/mips/kernel/topology.c
> @@ -5,6 +5,8 @@
>  #include <linux/node.h>
>  #include <linux/nodemask.h>
>  #include <linux/percpu.h>
> +#include <linux/seq_file.h>
> +#include <linux/smp.h>
>  
>  static DEFINE_PER_CPU(struct cpu, cpu_devices);
>  
> @@ -26,3 +28,97 @@ static int __init topology_init(void)
>  }
>  
>  subsys_initcall(topology_init);
> +
> +static struct kobj_type cpuregs_kobj_type = {
> +	.sysfs_ops = &kobj_sysfs_ops,
> +};
> +
> +struct cpureg {
> +	struct kobject kobj;
> +	struct cpuinfo_mips *info;
> +};
> +static DEFINE_PER_CPU(struct cpureg, cpuregs);

static kobjects are nothing you should ever create willingly.  That's a
dynamic reference counted structure being declared on the "stack"?

Please no.

thanks,

greg k-h
diff mbox series

Patch

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 5bf61881f012..adf855e7bb9b 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -512,6 +512,17 @@  Description:	information about CPUs heterogeneity.
 
 		cpu_capacity: capacity of cpuX.
 
+What:		/sys/devices/system/cpu/cpuX/regs/
+		/sys/devices/system/cpu/cpuX/regs/identification/
+		/sys/devices/system/cpu/cpuX/regs/identification/prid
+		/sys/devices/system/cpu/cpuX/regs/identification/globalnumber
+Date:		Augest 2022
+Contact:	Linux MIPS Kernel Mailing list <linux-mips@vger.kernel.org>
+Description:	MIPS CPU registers
+
+		'identification' directory exposes the Processor ID and Global Number
+		registers for identifying model and revision of the CPU.
+
 What:		/sys/devices/system/cpu/vulnerabilities
 		/sys/devices/system/cpu/vulnerabilities/meltdown
 		/sys/devices/system/cpu/vulnerabilities/spectre_v1
diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c
index 9429d85a4703..90b5136afb63 100644
--- a/arch/mips/kernel/topology.c
+++ b/arch/mips/kernel/topology.c
@@ -5,6 +5,8 @@ 
 #include <linux/node.h>
 #include <linux/nodemask.h>
 #include <linux/percpu.h>
+#include <linux/seq_file.h>
+#include <linux/smp.h>
 
 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 
@@ -26,3 +28,97 @@  static int __init topology_init(void)
 }
 
 subsys_initcall(topology_init);
+
+static struct kobj_type cpuregs_kobj_type = {
+	.sysfs_ops = &kobj_sysfs_ops,
+};
+
+struct cpureg {
+	struct kobject kobj;
+	struct cpuinfo_mips *info;
+};
+static DEFINE_PER_CPU(struct cpureg, cpuregs);
+
+#define kobj_to_cpureg(kobj)	container_of(kobj, struct cpureg, kobj)
+#define CPUREGS_ATTR_RO(_name, _field)						\
+	static ssize_t _name##_show(struct kobject *kobj,			\
+			struct kobj_attribute *attr, char *buf)			\
+	{									\
+		struct cpuinfo_mips *info = kobj_to_cpureg(kobj)->info;		\
+										\
+		return sprintf(buf, "0x%08x\n", info->_field);	\
+	}									\
+	static struct kobj_attribute cpuregs_attr_##_name = __ATTR_RO(_name)
+
+CPUREGS_ATTR_RO(prid, processor_id);
+CPUREGS_ATTR_RO(globalnumber, globalnumber);
+
+static struct attribute *cpuregs_id_attrs[] = {
+	&cpuregs_attr_prid.attr,
+	&cpuregs_attr_globalnumber.attr,
+	NULL
+};
+
+static const struct attribute_group cpuregs_attr_group = {
+	.attrs = cpuregs_id_attrs,
+	.name = "identification"
+};
+
+static int cpuregs_cpu_online(unsigned int cpu)
+{
+	int rc;
+	struct device *dev;
+	struct cpureg *reg = &per_cpu(cpuregs, cpu);
+
+	dev = get_cpu_device(cpu);
+	if (!dev) {
+		rc = -ENODEV;
+		goto out;
+	}
+	rc = kobject_add(&reg->kobj, &dev->kobj, "regs");
+	if (rc)
+		goto out;
+	rc = sysfs_create_group(&reg->kobj, &cpuregs_attr_group);
+	if (rc)
+		kobject_del(&reg->kobj);
+out:
+	return rc;
+}
+
+static int cpuregs_cpu_offline(unsigned int cpu)
+{
+	struct device *dev;
+	struct cpureg *reg = &per_cpu(cpuregs, cpu);
+
+	dev = get_cpu_device(cpu);
+	if (!dev)
+		return -ENODEV;
+	if (reg->kobj.parent) {
+		sysfs_remove_group(&reg->kobj, &cpuregs_attr_group);
+		kobject_del(&reg->kobj);
+	}
+
+	return 0;
+}
+
+static int __init cpuinfo_regs_init(void)
+{
+	int cpu, ret;
+
+	for_each_possible_cpu(cpu) {
+		struct cpureg *reg = &per_cpu(cpuregs, cpu);
+
+		reg->info = &cpu_data[cpu];
+		kobject_init(&reg->kobj, &cpuregs_kobj_type);
+	}
+
+	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mips/topology:online",
+				cpuregs_cpu_online, cpuregs_cpu_offline);
+	if (ret < 0) {
+		pr_err("cpuinfo: failed to register hotplug callbacks.\n");
+		return ret;
+	}
+	return 0;
+}
+
+device_initcall(cpuinfo_regs_init);