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Re: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI)

Started byDaniel Lezcano <daniel.lezcano@linaro.org>
First post2016-06-27 18:30 +0200
Last post2016-06-27 20:00 +0200
Articles 3 — 2 participants

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  Re: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI) Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-06-27 18:30 +0200
    Re: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI) Sudeep Holla <sudeep.holla@arm.com> - 2016-06-27 19:10 +0200
      Re: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI) Sudeep Holla <sudeep.holla@arm.com> - 2016-06-27 20:00 +0200

#1432150 — Re: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI)

FromDaniel Lezcano <daniel.lezcano@linaro.org>
Date2016-06-27 18:30 +0200
SubjectRe: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI)
Message-ID<rOHA6-2Ez-37@gated-at.bofh.it>
On 06/22/2016 04:17 PM, Lorenzo Pieralisi wrote:
> Hi Sudeep,
>
> On Tue, Jun 14, 2016 at 03:48:38PM +0100, Sudeep Holla wrote:
>> This patch adds appropriate callbacks to support ACPI Low Power Idle
>> (LPI) on ARM64.
>>
>> Now that arm_enter_idle_state is exactly same in both generic ARM{32,64}
>> CPUIdle driver and ARM64 backend for ACPI processor idle driver, we can
>> unify it and move to cpuidle-arm.h header.
>>
>> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>> Cc: linux-arm-kernel@lists.infradead.org
>> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>> ---
>>   arch/arm64/kernel/cpuidle.c   | 17 +++++++++++++
>>   drivers/cpuidle/cpuidle-arm.c | 23 ++----------------
>>   drivers/firmware/psci.c       | 56 +++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/cpuidle-arm.h   | 30 +++++++++++++++++++++++
>>   4 files changed, 105 insertions(+), 21 deletions(-)
>>   create mode 100644 include/linux/cpuidle-arm.h
>
> This patch seems fine by me, it would be good if Daniel can have
> a look too.
>
> Some minor comments below.
>
> [...]
>
>> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
>> index 03e04582791c..c6caa863d156 100644
>> --- a/drivers/firmware/psci.c
>> +++ b/drivers/firmware/psci.c
>> @@ -13,6 +13,7 @@
>>
>>   #define pr_fmt(fmt) "psci: " fmt
>>
>> +#include <linux/acpi.h>
>>   #include <linux/arm-smccc.h>
>>   #include <linux/cpuidle.h>
>>   #include <linux/errno.h>
>> @@ -310,11 +311,66 @@ static int psci_dt_cpu_init_idle(struct device_node *cpu_node, int cpu)
>>   	return ret;
>>   }
>>
>> +#ifdef CONFIG_ACPI
>> +#include <acpi/processor.h>
>> +
>> +static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
>> +{
>> +	int i, count;
>> +	u32 *psci_states;
>> +	struct acpi_processor *pr;
>> +	struct acpi_lpi_state *lpi;
>> +
>> +	pr = per_cpu(processors, cpu);
>> +	if (unlikely(!pr || !pr->flags.has_lpi))
>> +		return -EINVAL;
>> +
>> +	/*
>> +	 * If the PSCI cpu_suspend function hook has not been initialized
>> +	 * idle states must not be enabled, so bail out
>> +	 */
>> +	if (!psci_ops.cpu_suspend)
>> +		return -EOPNOTSUPP;
>> +
>> +	count = pr->power.count - 1;
>> +	if (count <= 0)
>> +		return -ENODEV;
>> +
>> +	psci_states = kcalloc(count, sizeof(*psci_states), GFP_KERNEL);
>> +	if (!psci_states)
>> +		return -ENOMEM;
>> +
>> +	for (i = 0; i < count; i++) {
>> +		u32 state;
>> +
>> +		lpi = &pr->power.lpi_states[i + 1];
>> +		state = lpi->address & 0xFFFFFFFF;

Why mask 'address' if 'state' is u32 ?

>> +		if (!psci_power_state_is_valid(state)) {
>> +			pr_warn("Invalid PSCI power state %#x\n", state);
>> +			kfree(psci_states);
>> +			return -EINVAL;
>> +		}
>> +		psci_states[i] = state;
>> +	}
>> +	/* Idle states parsed correctly, initialize per-cpu pointer */
>> +	per_cpu(psci_power_state, cpu) = psci_states;
>> +	return 0;

The ACPI and the PSCI code are not self contained here.

It would be nice to move this function to the ACPI code.

>> +}
>> +#else
>> +static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
>> +{
>> +	return -EINVAL;
>> +}
>> +#endif
>> +
>>   int psci_cpu_init_idle(unsigned int cpu)
>>   {
>>   	struct device_node *cpu_node;
>>   	int ret;
>>
>> +	if (!acpi_disabled)
>> +		return psci_acpi_cpu_init_idle(cpu);
>> +

acpi_disabled - acpi_disabled - acpi_disabled everywhere :/

The enable-method approach is not straightforward and now it is polluted 
by acpi-disabled.

So IIUC,

smp_init_cpus (contains acpi_disabled)
   smp_cpu_setup
     cpu_read_ops
       cpu_read_enable_method (contains acpi_disabled)
         acpi_get_enable_method (returns 'psci' after checking 
psci_is_present)

Then psci_cpu_init_idle is called... and check again acpi_disabled.

IMO, the circumlocution with the psci vs acpi vs acpi_disabled is 
getting unnecessary too complex, is prone to error and will lead to 
unmaintainable code very soon.

I suggest to sort out encapsulation and self-contained code before 
adding more feature in this area.


>>   	cpu_node = of_get_cpu_node(cpu, NULL);
>>   	if (!cpu_node)
>>   		return -ENODEV;
>> diff --git a/include/linux/cpuidle-arm.h b/include/linux/cpuidle-arm.h
>> new file mode 100644
>> index 000000000000..b99bcb3f43dd
>> --- /dev/null
>> +++ b/include/linux/cpuidle-arm.h
>
> arm-cpuidle.h for consistency with other (ARM) include/linux files ?
>
>> @@ -0,0 +1,30 @@
>> +#include <linux/cpu_pm.h>
>> +
>> +#include <asm/cpuidle.h>
>> +
>> +/*
>> + * arm_enter_idle_state - Programs CPU to enter the specified state
>> + */
>> +static int arm_generic_enter_idle_state(int idx)
>> +{
>> +	int ret;
>> +
>> +	if (!idx) {
>> +		cpu_do_idle();
>> +		return idx;
>> +	}
>> +
>> +	ret = cpu_pm_enter();
>> +	if (!ret) {
>> +		/*
>> +		 * Pass idle state index to cpu_suspend which in turn will
>> +		 * call the CPU ops suspend protocol with idle index as a
>> +		 * parameter.
>> +		 */
>> +		ret = arm_cpuidle_suspend(idx);
>> +
>> +		cpu_pm_exit();
>> +	}
>> +
>> +	return ret ? -1 : idx;
>> +}
>
> Either you do this, or we have to add it somehow somewhere in
> drivers/cpuidle to avoid duplicating it.
>
> @Daniel: do you have an opinion on this please ?

I don't like the idea to add an ARM arch specific header in 
include/linux. I thought this directory was supposed to contain as much 
as possible arch agnostic headers.

May be the name can be changed to something more generic:

eg.

int cpuidle_generic_enter(int idx);

and then add an option:

HAVE_CPUIDLE_GENERIC_ENTER

, then in the generic header:

#ifdef HAVE_CPUIDLE_GENERIC_ENTER
int cpuidle_generic_enter(int idx);
#endif

, change the function name in cpuidle-arm .c

and finally add in the ARM and ARM64 Kconfig's option 
HAVE_CPUIDLE_GENERIC_ENTER.


   -- Daniel

-- 
  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
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#1432162

FromSudeep Holla <sudeep.holla@arm.com>
Date2016-06-27 19:10 +0200
Message-ID<rOIcN-39i-1@gated-at.bofh.it>
In reply to#1432150

On 27/06/16 17:29, Daniel Lezcano wrote:
> On 06/22/2016 04:17 PM, Lorenzo Pieralisi wrote:
>> Hi Sudeep,
>>
>> On Tue, Jun 14, 2016 at 03:48:38PM +0100, Sudeep Holla wrote:
>>> This patch adds appropriate callbacks to support ACPI Low Power Idle
>>> (LPI) on ARM64.
>>>
>>> Now that arm_enter_idle_state is exactly same in both generic ARM{32,64}
>>> CPUIdle driver and ARM64 backend for ACPI processor idle driver, we can
>>> unify it and move to cpuidle-arm.h header.
>>>
>>> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
>>> Cc: Mark Rutland <mark.rutland@arm.com>
>>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>>> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>>> Cc: linux-arm-kernel@lists.infradead.org
>>> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>>> ---
>>>   arch/arm64/kernel/cpuidle.c   | 17 +++++++++++++
>>>   drivers/cpuidle/cpuidle-arm.c | 23 ++----------------
>>>   drivers/firmware/psci.c       | 56
>>> +++++++++++++++++++++++++++++++++++++++++++
>>>   include/linux/cpuidle-arm.h   | 30 +++++++++++++++++++++++
>>>   4 files changed, 105 insertions(+), 21 deletions(-)
>>>   create mode 100644 include/linux/cpuidle-arm.h
>>
>> This patch seems fine by me, it would be good if Daniel can have
>> a look too.
>>
>> Some minor comments below.
>>
>> [...]
>>
>>> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
>>> index 03e04582791c..c6caa863d156 100644
>>> --- a/drivers/firmware/psci.c
>>> +++ b/drivers/firmware/psci.c
>>> @@ -13,6 +13,7 @@
>>>
>>>   #define pr_fmt(fmt) "psci: " fmt
>>>
>>> +#include <linux/acpi.h>
>>>   #include <linux/arm-smccc.h>
>>>   #include <linux/cpuidle.h>
>>>   #include <linux/errno.h>
>>> @@ -310,11 +311,66 @@ static int psci_dt_cpu_init_idle(struct
>>> device_node *cpu_node, int cpu)
>>>       return ret;
>>>   }
>>>
>>> +#ifdef CONFIG_ACPI
>>> +#include <acpi/processor.h>
>>> +
>>> +static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
>>> +{
>>> +    int i, count;
>>> +    u32 *psci_states;
>>> +    struct acpi_processor *pr;
>>> +    struct acpi_lpi_state *lpi;
>>> +
>>> +    pr = per_cpu(processors, cpu);
>>> +    if (unlikely(!pr || !pr->flags.has_lpi))
>>> +        return -EINVAL;
>>> +
>>> +    /*
>>> +     * If the PSCI cpu_suspend function hook has not been initialized
>>> +     * idle states must not be enabled, so bail out
>>> +     */
>>> +    if (!psci_ops.cpu_suspend)
>>> +        return -EOPNOTSUPP;
>>> +
>>> +    count = pr->power.count - 1;
>>> +    if (count <= 0)
>>> +        return -ENODEV;
>>> +
>>> +    psci_states = kcalloc(count, sizeof(*psci_states), GFP_KERNEL);
>>> +    if (!psci_states)
>>> +        return -ENOMEM;
>>> +
>>> +    for (i = 0; i < count; i++) {
>>> +        u32 state;
>>> +
>>> +        lpi = &pr->power.lpi_states[i + 1];
>>> +        state = lpi->address & 0xFFFFFFFF;
>
> Why mask 'address' if 'state' is u32 ?
>

Agreed, I overlooked it.

>>> +        if (!psci_power_state_is_valid(state)) {
>>> +            pr_warn("Invalid PSCI power state %#x\n", state);
>>> +            kfree(psci_states);
>>> +            return -EINVAL;
>>> +        }
>>> +        psci_states[i] = state;
>>> +    }
>>> +    /* Idle states parsed correctly, initialize per-cpu pointer */
>>> +    per_cpu(psci_power_state, cpu) = psci_states;
>>> +    return 0;
>
> The ACPI and the PSCI code are not self contained here.
>
> It would be nice to move this function to the ACPI code.
>
>>> +}
>>> +#else
>>> +static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
>>> +{
>>> +    return -EINVAL;
>>> +}
>>> +#endif
>>> +
>>>   int psci_cpu_init_idle(unsigned int cpu)
>>>   {
>>>       struct device_node *cpu_node;
>>>       int ret;
>>>
>>> +    if (!acpi_disabled)
>>> +        return psci_acpi_cpu_init_idle(cpu);
>>> +
>
> acpi_disabled - acpi_disabled - acpi_disabled everywhere :/
>
> The enable-method approach is not straightforward and now it is polluted
> by acpi-disabled.
>
> So IIUC,
>
> smp_init_cpus (contains acpi_disabled)
>    smp_cpu_setup
>      cpu_read_ops
>        cpu_read_enable_method (contains acpi_disabled)
>          acpi_get_enable_method (returns 'psci' after checking
> psci_is_present)
>
> Then psci_cpu_init_idle is called... and check again acpi_disabled.
>
> IMO, the circumlocution with the psci vs acpi vs acpi_disabled is
> getting unnecessary too complex, is prone to error and will lead to
> unmaintainable code very soon.
>
> I suggest to sort out encapsulation and self-contained code before
> adding more feature in this area.
>

I understand your concern but I have no idea on how to clean up. Lorenzo
asked to factor our common code between psci_{dt,acpi}_cpu_init_idle and
I think you might not like the refactoring[1]. I didn't want to change
cpuidle_ops and hence psci_dt_cpu_init_idle parameters. I will see if
changing that simplifies things.

>>>       cpu_node = of_get_cpu_node(cpu, NULL);
>>>       if (!cpu_node)
>>>           return -ENODEV;
>>> diff --git a/include/linux/cpuidle-arm.h b/include/linux/cpuidle-arm.h
>>> new file mode 100644
>>> index 000000000000..b99bcb3f43dd
>>> --- /dev/null
>>> +++ b/include/linux/cpuidle-arm.h
>>
>> arm-cpuidle.h for consistency with other (ARM) include/linux files ?
>>
>>> @@ -0,0 +1,30 @@
>>> +#include <linux/cpu_pm.h>
>>> +
>>> +#include <asm/cpuidle.h>
>>> +
>>> +/*
>>> + * arm_enter_idle_state - Programs CPU to enter the specified state
>>> + */
>>> +static int arm_generic_enter_idle_state(int idx)
>>> +{
>>> +    int ret;
>>> +
>>> +    if (!idx) {
>>> +        cpu_do_idle();
>>> +        return idx;
>>> +    }
>>> +
>>> +    ret = cpu_pm_enter();
>>> +    if (!ret) {
>>> +        /*
>>> +         * Pass idle state index to cpu_suspend which in turn will
>>> +         * call the CPU ops suspend protocol with idle index as a
>>> +         * parameter.
>>> +         */
>>> +        ret = arm_cpuidle_suspend(idx);
>>> +
>>> +        cpu_pm_exit();
>>> +    }
>>> +
>>> +    return ret ? -1 : idx;
>>> +}
>>
>> Either you do this, or we have to add it somehow somewhere in
>> drivers/cpuidle to avoid duplicating it.
>>
>> @Daniel: do you have an opinion on this please ?
>
> I don't like the idea to add an ARM arch specific header in
> include/linux. I thought this directory was supposed to contain as much
> as possible arch agnostic headers.
>

While I agree, but what we have is ARM specific code here and calling it
generic might not make it any usable on other architecture unless they 
have the same semantics. I am fine if you and Rafael are OK with that.

> May be the name can be changed to something more generic:
>
> eg.
>
> int cpuidle_generic_enter(int idx);
>
> and then add an option:
>
> HAVE_CPUIDLE_GENERIC_ENTER
>
> , then in the generic header:
>
> #ifdef HAVE_CPUIDLE_GENERIC_ENTER
> int cpuidle_generic_enter(int idx);
> #endif
>
> , change the function name in cpuidle-arm .c
>
> and finally add in the ARM and ARM64 Kconfig's option
> HAVE_CPUIDLE_GENERIC_ENTER.
>
>
>    -- Daniel
>

[1] 
http://git.kernel.org/cgit/linux/kernel/git/sudeep.holla/linux.git/commit/?h=for_review/arm64_lpi&id=9b516ad4442b4168e962ba4ca87bd568d605053b
-- 
Regards,
Sudeep

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#1432204

FromSudeep Holla <sudeep.holla@arm.com>
Date2016-06-27 20:00 +0200
Message-ID<rOIZc-3tG-33@gated-at.bofh.it>
In reply to#1432162

On 27/06/16 18:07, Sudeep Holla wrote:
>
>
> On 27/06/16 17:29, Daniel Lezcano wrote:

[...]

>>
>> acpi_disabled - acpi_disabled - acpi_disabled everywhere :/
>>
>> The enable-method approach is not straightforward and now it is polluted
>> by acpi-disabled.
>>
>> So IIUC,
>>
>> smp_init_cpus (contains acpi_disabled)
>>    smp_cpu_setup
>>      cpu_read_ops
>>        cpu_read_enable_method (contains acpi_disabled)
>>          acpi_get_enable_method (returns 'psci' after checking
>> psci_is_present)
>>
>> Then psci_cpu_init_idle is called... and check again acpi_disabled.
>>
>> IMO, the circumlocution with the psci vs acpi vs acpi_disabled is
>> getting unnecessary too complex, is prone to error and will lead to
>> unmaintainable code very soon.
>>
>> I suggest to sort out encapsulation and self-contained code before
>> adding more feature in this area.
>>
>
> I understand your concern but I have no idea on how to clean up. Lorenzo
> asked to factor our common code between psci_{dt,acpi}_cpu_init_idle and
> I think you might not like the refactoring[1]. I didn't want to change
> cpuidle_ops and hence psci_dt_cpu_init_idle parameters. I will see if
> changing that simplifies things.
>

One of the reasons for adding acpi_disabled check is to keep the other
logic at the same place. Otherwise we end up duplicating that code which
is what I have done in psci_{dt,acpi}_cpu_init_idle at the first place.

-- 
Regards,
Sudeep

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