[2/6] ARM: cpuidle: Add a cpuidle ops structure to be used for DT

Message ID 1425385777-14766-3-git-send-email-daniel.lezcano@linaro.org
State New
Headers show

Commit Message

Daniel Lezcano March 3, 2015, 12:29 p.m.
The current state of the different cpuidle drivers is the different PM
operations are passed via the platform_data using the platform driver
paradigm.

This approach allowed to split the low level PM code from the arch specific
and the generic cpuidle code.

Unfortunately there are complains about this approach as, in the context of the
single kernel image, we have multiple drivers loaded in memory for nothing and
the platform driver is not adequate for cpuidle.

This patch provides a common interface via cpuidle ops for all new cpuidle
driver and a definition for the device tree.

It will allow with the next patches to a have a common definition with ARM64
and share the same cpuidle driver.

The code is optimized to use the __init section intensively in order to reduce
the memory footprint after the driver is initialized and unify the function
names with ARM64.

In order to prevent multiple declarations and the specific cpuidle ops to be
spread across the different headers, a mechanism, similar to the cgroup subsys,
has been introduced.

A new platform willing to add its cpuidle ops must add an entry in the file
cpuidle_ops.h in the current form:

 #if IS_ENABLED(CONFIG_ARM_FOO_CPUIDLE)
 CPUIDLE_OPS(foo)
 #endif

... and use the variable name in the specific low level code:

struct cpuidle_ops foo_cpuidle_ops;

The CPUIDLE_OPS macro will be processed in different way in the cpuidle.c file,
thus allowing to keep untouched the arm cpuidle core code in the future when
a new platform is added.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 arch/arm/include/asm/cpuidle.h     | 10 +++++
 arch/arm/include/asm/cpuidle_ops.h |  3 ++
 arch/arm/kernel/cpuidle.c          | 85 ++++++++++++++++++++++++++++++++++++++
 arch/arm64/include/asm/cpuidle.h   |  5 ++-
 4 files changed, 102 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm/include/asm/cpuidle_ops.h

Comments

Daniel Lezcano March 17, 2015, 11:01 a.m. | #1
On 03/16/2015 07:16 PM, Lorenzo Pieralisi wrote:
> On Tue, Mar 03, 2015 at 12:29:33PM +0000, Daniel Lezcano wrote:
>> The current state of the different cpuidle drivers is the different PM
>
> Nit: "The current state of cpuidle drivers is such that different ..."

Ok.

>> operations are passed via the platform_data using the platform driver
>> paradigm.
>>
>> This approach allowed to split the low level PM code from the arch specific
>> and the generic cpuidle code.
>>
>> Unfortunately there are complains about this approach as, in the context of the
>
> Nit: s/complains/complaints

Ok.

[ ... ]

>> @@ -27,4 +27,14 @@ static inline int arm_cpuidle_simple_enter(struct cpuidle_device *dev,
>>    */
>>   #define ARM_CPUIDLE_WFI_STATE ARM_CPUIDLE_WFI_STATE_PWR(UINT_MAX)
>>
>> +struct cpuidle_ops {
>> +	const char *name;
>> +	int (*suspend)(int cpu, unsigned long arg);
>> +	int (*init)(struct device_node *, int cpu);
>> +};
>> +
>> +extern int arm_cpuidle_suspend(int index);
>> +
>> +extern int arm_cpuidle_init(int cpu);
>
> idle_cpu_suspend()
> idle_cpu_init()
>
> ?
>
> I am really not fussed about the naming.
>
> To make this and x86 driver name compliant (well, function signatures
> are a bit different) we could use:
>
> arm_idle()
> arm_idle_cpu_init()
>
> even though I think the arch prefix is useless.
>
> Side note: why is the x86 driver in drivers/idle ? To have another dir :) ?

I believe it is there for historical reasons.

[ ... ]

>> +static struct cpuidle_ops cpuidle_ops[NR_CPUS];
>
> That's because you want platform cpuidle_ops to be __initdata ?

Yes.

> It should not be a big overhead on arm32 to have a number of
> structs equal to NR_CPUS, on arm64 it is the other way around
> there are few cpu_ops, but number of CPUs can be high so it
> is an array of pointers.
>
> I think it is ok to leave it as it is (or probably make cpuidle_ops
> a single struct, I expect enable-method to be common across cpus).

I prefer to keep per cpu because I am not sure of this assumption.

[ ... ]

>> +	cpuidle_ops[cpu] = *ops; /* structure copy */
>
> See above.
>
>> +
>> +	pr_notice("cpuidle: enable-method property '%s'"
>> +		  " found operations\n", ops->name);
>> +
>> +	return 0;
>> +}
>> +
>> +int __init arm_cpuidle_init(int cpu)
>> +{
>> +	int ret = -EOPNOTSUPP;
>
> Nit: You always assign ret, so there is no point in initializing it.

Ok, I will fix it.

Thanks for reviewing.

   -- Daniel
Daniel Lezcano March 18, 2015, 8:13 a.m. | #2
On 03/18/2015 02:14 AM, Stephen Boyd wrote:
> On 03/17/15 04:29, Lorenzo Pieralisi wrote:
>> On Mon, Mar 16, 2015 at 10:08:19PM +0000, Stephen Boyd wrote:
>>> On 03/03/15 04:29, Daniel Lezcano wrote:
>>>> The code is optimized to use the __init section intensively in order to reduce
>>>> the memory footprint after the driver is initialized and unify the function
>>>> names with ARM64.
>>>>
>>>> In order to prevent multiple declarations and the specific cpuidle ops to be
>>>> spread across the different headers, a mechanism, similar to the cgroup subsys,
>>>> has been introduced.
>>>>
>>>> A new platform willing to add its cpuidle ops must add an entry in the file
>>>> cpuidle_ops.h in the current form:
>>>>
>>>>   #if IS_ENABLED(CONFIG_ARM_FOO_CPUIDLE)
>>>>   CPUIDLE_OPS(foo)
>>>>   #endif
>>>>
>>>> ... and use the variable name in the specific low level code:
>>>>
>>>> struct cpuidle_ops foo_cpuidle_ops;
>>>>
>>>> The CPUIDLE_OPS macro will be processed in different way in the cpuidle.c file,
>>>> thus allowing to keep untouched the arm cpuidle core code in the future when
>>>> a new platform is added.
>>> [...]
>>>> diff --git a/arch/arm/include/asm/cpuidle_ops.h b/arch/arm/include/asm/cpuidle_ops.h
>>>> new file mode 100644
>>>> index 0000000..be0a612
>>>> --- /dev/null
>>>> +++ b/arch/arm/include/asm/cpuidle_ops.h
>>>> @@ -0,0 +1,3 @@
>>>> +/*
>>>> + * List of cpuidle operations
>>>> + */
>>>> diff --git a/arch/arm/kernel/cpuidle.c b/arch/arm/kernel/cpuidle.c
>>>> index 45969f8..25e9789c 100644
>>>> --- a/arch/arm/kernel/cpuidle.c
>>>> +++ b/arch/arm/kernel/cpuidle.c
>>>> @@ -10,8 +10,29 @@
>>>>    */
>>>>
>>>>   #include <linux/cpuidle.h>
>>>> +#include <linux/of.h>
>>>> +#include <linux/of_device.h>
>>>>   #include <asm/cpuidle.h>
>>>>
>>>> +#define CPUIDLE_OPS(__x) extern struct cpuidle_ops __x ## _cpuidle_ops;
>>>> +#include <asm/cpuidle_ops.h>
>>>> +#undef CPUIDLE_OPS
>>>> +
>>>> +#define CPUIDLE_OPS(__x) __x ## _cpuidle_ops_id,
>>>> +enum cpuidle_ops_id {
>>>> +#include <asm/cpuidle_ops.h>
>>>> +        CPUIDLE_OPS_COUNT,
>>>> +};
>>>> +#undef CPUIDLE_OPS
>>>> +
>>>> +#define CPUIDLE_OPS(__x) [__x ## _cpuidle_ops_id ] = &__x ## _cpuidle_ops,
>>>> +static struct cpuidle_ops *supported_cpuidle_ops[] __initconst = {
>>>> +#include <asm/cpuidle_ops.h>
>>>> +};
>>>> +#undef CPUIDLE_OPS
>>>> +
>>>> +static struct cpuidle_ops cpuidle_ops[NR_CPUS];
>>> Is there any reason why we aren't putting these structures into a linker
>>> section like we do for the smp operations structures?
>> I think it can be done with an OF_TABLE, it is a bit of shame cpuidle_ops
>> should work on UP too otherwise they could have been merged in
>> smp_ops to create cpu_ops, like arm64 does.
>
> We should merge the two and remove the SMP dependency on arm32.

I will be happy to do that but right now it would be nice to keep 
focused on bringing the cpuidle ops first, even if we have a bit of code 
duplicated, in order to unblock the cpuidle drivers awaiting for this 
code to be merged.

>>> The nice thing about using the linker is it makes it clearer at the
>>> location where we define the structure that it's actually used by
>>> something. Right now the structures are defined non-static in a file and
>>> then we have to know that a CPUIDLE_OPS() define has been made in
>>> another architecture specific asm header file so that this macro magic
>>> works. The commit text says something about multiple declarations and
>>> ops spread across header files, which shouldn't apply if we're using the
>>> linker to find these ops and merge them into an array we can iterate over.
>> It makes sense, see above for UP vs SMP. I wonder if we can't find
>> something to overcome the UP limitation nicely, the init code in
>> arch/arm/kernel/devtree.c is identical for smp_ops and cpuidle_ops,
>> apart from the CONFIG_SMP ifdeffery.
>
> It should be possible to replace the arm32 smp_operations structure with
> something like the arm64 cpu_operations structure. Yes we would have to
> drop the SMP dependency, but that will be ok. It would require some work
> to make arm32 and arm64 the same, but for these purposes that isn't
> really required as long as we can put the cpu idle hook there.
>

Patch

diff --git a/arch/arm/include/asm/cpuidle.h b/arch/arm/include/asm/cpuidle.h
index 348dc81..3d31459 100644
--- a/arch/arm/include/asm/cpuidle.h
+++ b/arch/arm/include/asm/cpuidle.h
@@ -27,4 +27,14 @@  static inline int arm_cpuidle_simple_enter(struct cpuidle_device *dev,
  */
 #define ARM_CPUIDLE_WFI_STATE ARM_CPUIDLE_WFI_STATE_PWR(UINT_MAX)
 
+struct cpuidle_ops {
+	const char *name;
+	int (*suspend)(int cpu, unsigned long arg);
+	int (*init)(struct device_node *, int cpu);
+};
+
+extern int arm_cpuidle_suspend(int index);
+
+extern int arm_cpuidle_init(int cpu);
+
 #endif
diff --git a/arch/arm/include/asm/cpuidle_ops.h b/arch/arm/include/asm/cpuidle_ops.h
new file mode 100644
index 0000000..be0a612
--- /dev/null
+++ b/arch/arm/include/asm/cpuidle_ops.h
@@ -0,0 +1,3 @@ 
+/*
+ * List of cpuidle operations
+ */
diff --git a/arch/arm/kernel/cpuidle.c b/arch/arm/kernel/cpuidle.c
index 45969f8..25e9789c 100644
--- a/arch/arm/kernel/cpuidle.c
+++ b/arch/arm/kernel/cpuidle.c
@@ -10,8 +10,29 @@ 
  */
 
 #include <linux/cpuidle.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 #include <asm/cpuidle.h>
 
+#define CPUIDLE_OPS(__x) extern struct cpuidle_ops __x ## _cpuidle_ops;
+#include <asm/cpuidle_ops.h>
+#undef CPUIDLE_OPS
+
+#define CPUIDLE_OPS(__x) __x ## _cpuidle_ops_id,
+enum cpuidle_ops_id {
+#include <asm/cpuidle_ops.h>
+        CPUIDLE_OPS_COUNT,
+};
+#undef CPUIDLE_OPS
+
+#define CPUIDLE_OPS(__x) [__x ## _cpuidle_ops_id ] = &__x ## _cpuidle_ops,
+static struct cpuidle_ops *supported_cpuidle_ops[] __initconst = {
+#include <asm/cpuidle_ops.h>
+};
+#undef CPUIDLE_OPS
+
+static struct cpuidle_ops cpuidle_ops[NR_CPUS];
+
 int arm_cpuidle_simple_enter(struct cpuidle_device *dev,
 		struct cpuidle_driver *drv, int index)
 {
@@ -19,3 +40,67 @@  int arm_cpuidle_simple_enter(struct cpuidle_device *dev,
 
 	return index;
 }
+
+int arm_cpuidle_suspend(int index)
+{
+	int ret = -EOPNOTSUPP;
+	int cpu = smp_processor_id();
+
+	if (cpuidle_ops[cpu].suspend)
+		ret = cpuidle_ops[cpu].suspend(cpu, index);
+
+	return ret;
+}
+
+static struct cpuidle_ops *__init arm_cpuidle_get_ops(const char *name)
+{
+	int i;
+
+	for (i = 0; i < CPUIDLE_OPS_COUNT; i++) {
+		if (!strcmp(name, supported_cpuidle_ops[i]->name))
+			return supported_cpuidle_ops[i];
+	}
+
+	return NULL;
+}
+
+static int __init arm_cpuidle_read_ops(struct device_node *dn, int cpu)
+{
+	const char *enable_method;
+	struct cpuidle_ops *ops;
+
+	enable_method = of_get_property(dn, "enable-method", NULL);
+	if (!enable_method)
+		return -ENOENT;
+
+	ops = arm_cpuidle_get_ops(enable_method);
+	if (!ops) {
+		pr_warn("%s: unsupported enable-method property: %s\n",
+			dn->full_name, enable_method);
+		return -EOPNOTSUPP;
+	}
+
+	cpuidle_ops[cpu] = *ops; /* structure copy */
+
+	pr_notice("cpuidle: enable-method property '%s'"
+		  " found operations\n", ops->name);
+
+	return 0;
+}
+
+int __init arm_cpuidle_init(int cpu)
+{
+	int ret = -EOPNOTSUPP;
+	struct device_node *cpu_node = of_cpu_device_node_get(cpu);
+
+	if (!cpu_node)
+		return -ENODEV;
+
+	ret = arm_cpuidle_read_ops(cpu_node, cpu);
+	if (!ret && cpuidle_ops[cpu].init)
+		ret = cpuidle_ops[cpu].init(cpu_node, cpu);
+
+	of_node_put(cpu_node);
+
+	return ret;
+}
diff --git a/arch/arm64/include/asm/cpuidle.h b/arch/arm64/include/asm/cpuidle.h
index 0710654..1bee287 100644
--- a/arch/arm64/include/asm/cpuidle.h
+++ b/arch/arm64/include/asm/cpuidle.h
@@ -15,5 +15,8 @@  static inline int cpu_suspend(unsigned long arg)
 	return -EOPNOTSUPP;
 }
 #endif
-
+static inline int arm_cpuidle_suspend(int index)
+{
+	return cpu_suspend(index);
+}
 #endif