[PATCH v14 03/10] qcom: spm: Add Subsystem Power Manager driver

Lina Iyer
2014-12-04T16:28:34Z

On Thu, Dec 04 2014 at 02:02 -0700, Arnd Bergmann wrote:
>On Thursday 04 December 2014 09:52:39 Daniel Lezcano wrote:
>> On 12/03/2014 09:35 PM, Arnd Bergmann wrote:
>> > On Wednesday 03 December 2014 07:31:22 Lina Iyer wrote:
>> >>>>> +static int __init qcom_spm_init(void)
>> >>>>> +{
>> >>>>> + int ret;
>> >>>>> +
>> >>>>> + /*
>> >>>>> + * cpuidle driver need to registered before the cpuidle device
>> >>>>> + * for any cpu. Register the device for the the cpuidle driver.
>> >>>>> + */
>> >>>>> + ret = platform_device_register(&qcom_cpuidle_drv);
>> >>>>> + if (ret)
>> >>>>> + return ret;
>> >>>> Stephen pointed out that we would have the platform device lying around
>> >>>> on a non-QCOM device when using multi_v7_defconfig.
>> >>>
>> >>> Perhaps I am missing the point, but this is not supposed to happen, no ?
>> >>>
>> >> This would happen, since the file would compile on multi_v7 and we would
>> >> initialize and register this device regardless. The cpuidle-qcom.c
>> >> driver probe would bail out looking for a matching compatible property.
>> >> So we would not register a cpuidle driver but the device would lay
>> >> around.
>> >
>> > I think the problem is registering a platform_device. I've complained
>> > about this before, but it still seems to get copied all over the
>> > place. Please don't do this but have a driver that looks at DT to
>> > figure out whether to access hardware or not.
>>
>> We did this approach but, I can remember why, someone was complaining
>> about it also
>>
>> The platform device/driver paradigm allowed us to split the arch
>> specific parts by passing the pm ops through the platform data.
>>
>> Would make sense to have a single common place for the ARM arch where we
>> initialize the platform device for cpuidle ?
>
>No. It's really not a device, and if you pretend that it is, you get
>into problems like this.

Arnd, the problem is that the provides function pointers to the SoC code
that the cpuilde driver uses to call based on the idle state.

After much discussions, we came down to using function pointers from
translating from DT strings, other than using that again, I dont see a
good way of achieving the ability of cpuidle driver staying a separate
driver from the SPM driver.

Daniel, thoughts?