Re: [V4 patch 03/15] cpuidle: make a single register function for all

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On 04/23/2013 02:32 PM, Santosh Shilimkar wrote:
> On Tuesday 23 April 2013 02:24 PM, Daniel Lezcano wrote:
>> The usual scheme to initialize a cpuidle driver on a SMP is:
>>
>> 	cpuidle_register_driver(drv);
>> 	for_each_possible_cpu(cpu) {
>> 		device = &per_cpu(cpuidle_dev, cpu);
>> 		cpuidle_register_device(device);
>> 	}
>>
>> This code is duplicated in each cpuidle driver.
>>
>> On UP systems, it is done this way:
>>
>> 	cpuidle_register_driver(drv);
>> 	device = &per_cpu(cpuidle_dev, cpu);
>> 	cpuidle_register_device(device);
>>
>> On UP, the macro 'for_each_cpu' does one iteration:
>>
>> #define for_each_cpu(cpu, mask)                 \
>>         for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
>>
>> Hence, the initialization loop is the same for UP than SMP.
>>
>> Beside, we saw different bugs / mis-initialization / return code unchecked in
>> the different drivers, the code is duplicated including bugs. After fixing all
>> these ones, it appears the initialization pattern is the same for everyone.
>>
>> Please note, some drivers are doing dev->state_count = drv->state_count. This is
>> not necessary because it is done by the cpuidle_enable_device function in the
>> cpuidle framework. This is true, until you have the same states for all your
>> devices. Otherwise, the 'low level' API should be used instead with the specific
>> initialization for the driver.
>>
>> Let's add a wrapper function doing this initialization with a cpumask parameter
>> for the coupled idle states and use it for all the drivers.
>>
>> That will save a lot of LOC, consolidate the code, and the modifications in the
>> future could be done in a single place. Another benefit is the consolidation of
>> the cpuidle_device variable which is now in the cpuidle framework and no longer
>> spread accross the different arch specific drivers.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
>> ---
> 
> I don't see you have addressed the comment on V3 [1] i gave for the subject patch
> Any reason ?

Yes, sorry for not answering.

This modification should be handled in the __cpuidle_register_device
function.

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 49e8d30..936d862 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -372,7 +372,7 @@ static int __cpuidle_register_device(struct
cpuidle_device *dev)
        int ret;
        struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

-       if (!try_module_get(drv->owner))
+       if (!drv || !try_module_get(drv->owner))
                return -EINVAL;

        per_cpu(cpuidle_devices, dev->cpu) = dev;

Thus, the cpuidle_register function is not impacted by this as it will
always do cpuidle_register_driver, followed by cpuidle_register_device.

  -- Daniel

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