[PATCH 08/10] ARM: clps711x: Add CLPS711X cpuidle driver

[Daniel Lezcano]

On 07/21/2013 06:11 AM, Alexander Shiyan wrote:
> On Sat, 20 Jul 2013 23:42:11 +0200
> Daniel Lezcano <daniel.lezcano at linaro.org> wrote:
> 
>> On 07/18/2013 08:34 PM, Alexander Shiyan wrote:
>>> This adds the cpuidle driver for Cirrus Logic CLPS711X series SoCs.
>>> Designed primarily for migration CLPS711X subarch for multiplatform & DT.
>>>
>>> Signed-off-by: Alexander Shiyan <shc_work at mail.ru>
>>> ---
>>>  drivers/cpuidle/Kconfig            |  6 +++
>>>  drivers/cpuidle/Makefile           |  1 +
>>>  drivers/cpuidle/cpuidle-clps711x.c | 80 ++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 87 insertions(+)
>>>  create mode 100644 drivers/cpuidle/cpuidle-clps711x.c
> [...]
>>> +static int clps711x_cpuidle_halt(struct cpuidle_device *dev,
>>> +				 struct cpuidle_driver *drv, int index)
>>> +{
>>> +	writel(1, clps711x_halt);
>>
>> In what the 'clps711x_halt' differs from the usual WFI (cpu_do_idle) ?
> 
> AFAIK, ARM720T does not implement the WFI instruction.
> "HALT" register in CLPS711X do the same:
> "A write to this location will put the system into the Idle State by
> halting the clock to the processor until an interrupt is generated."

I am wondering if you are not using more states, may be you can consider
to add a clps711x idle function for the 'arm_pm_idle' callback instead
of creating a new driver.

>>> +	asm volatile ("mov r0, r0");
>>> +	asm volatile ("mov r0, r0");
>>
>> Why are needed these two volatile ?
> 
> Two NOP instructions necessary following the enable or disable of the MMU.
> Documentation not say anything about using this for "HALT", maybe it's the
> remnants of the old code. I will remove it.

Ok.

> [...]
>>> +static int clps711x_cpuidle_remove(struct platform_device *pdev)
>>> +{
>>> +	cpuidle_unregister(&clps711x_idle_driver);
>>> +
>>> +	return 0;
>>> +}
>>
>> The driver is not compiled as module, will this function be called ?
> 
> You're right. I will remove it.
> 
>>> +static const struct of_device_id clps711x_cpuidle_dt_ids[] = {
>>> +	{ .compatible = "cirrus,clps711x-cpuidle", },
>>> +	{ }
>>> +};
>>> +MODULE_DEVICE_TABLE(of, clps711x_cpuidle_dt_ids);
>>> +
>>> +static struct platform_driver clps711x_cpuidle_driver = {
>>> +	.driver	= {
>>> +		.name		= "clps711x-cpuidle",
>>> +		.owner		= THIS_MODULE,
>>> +		.of_match_table	= clps711x_cpuidle_dt_ids,
>>> +	},
>>> +	.remove	= clps711x_cpuidle_remove,
>>> +};
>>> +module_platform_driver_probe(clps711x_cpuidle_driver, clps711x_cpuidle_probe);
>>
>> +1
> 
> ??? What here?

I like the approach :)

Thanks
  -- Daniel


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