Re: domain off

[Krzysztof Kozlowski <k.kozlowski@samsung.com>]

On 20.01.2016 18:52, Sriram V wrote:
> Hi Krzyszof,
> 
> 
> 
> On Mon, Jan 11, 2016 at 7:51 AM, Krzysztof Kozlowski
> <k.kozlowski@samsung.com> wrote:
>> On 11.01.2016 10:48, Sriram V wrote:
>>> Hi Krzystof,
>>>
>>>
>>>
>>> On Mon, Jan 11, 2016 at 4:57 AM, Krzysztof Kozlowski
>>> <k.kozlowski@samsung.com> wrote:
>>>> 2016-01-10 22:49 GMT+09:00 Sriram V <vshrirama@gmail.com>:
>>>>> Hi Krzysztof,
>>>>>
>>>>> I see that in pm_genpd_sumarry, the domains are off. However, i still
>>>>> see the clocks are on.
>>>>> For example; isp and cam is turned off in pm_genpd_summary, however
>>>>> cam clocks are still on.
>>>>>
>>>>> Should'nt the clocks be turned off first and then the domain.
>>>>
>>>> No, the clocks in clock hierarchy are usually not disabled as a part
>>>> of domain power off. However respective drivers attached to a power
>>>> domain, when entering runtime suspend, should disable these clocks.
>>>>
>>>
>>> That is true, runtime suspend framework should disable the clocks.
>>> Hence, my question is if the clocks are active, Will disabling the
>>> domain take effect? Because when i print the status - they show that
>>> the domain is OFF.
>>
>> Yes, the domain will be disabled.
>>
>>>
>>> On my system, what i see is camera clocks are active, But the domain
>>> is OFF. Hence, i am not sure if camera subsystem is consuming power or
>>> not since clocks are on.
>>>
>>> >From my understanding, the domain status should not indicate OFF if
>>> any clocks are still on.
>>
>> Clocks and power domains in Linux are (mostly) independent subsystems so
>> the domain will be disabled even though some clocks are active. Some
>> clocks may be even missing in Linux (not defined) - it doesn't matter...
>>
>> It doesn't matter except in all the cases when this is a bug. :) The
>> clocks should be disabled and some muxes reparented to oscclk. One of
>> the cases we had was hang on reading clk_summary when power domain is off.
>>
> 
> Thanks for your pointers.
> 
> When i boot the kernel, I see that the following domains are currently
> on. I see that the following domains are currently on, Linux does not
> know about these domains and they are permanently on.
> 
> pd-fsys, pd-psgen, pd-peric, pd-wcore
> 
> Is there a way of finding out if these can be shut off. i dont think
> if clocks for the IP's serviced by these domains and the domain itself
> is correctly tied-in in runtime-pm. As these domains are always on.

The datasheet/reference manual in the "Local power control" describes
conditions whether they could be disabled or not. It also documents what
is required to power off them.

> 
> Also, what kernel are you using?

Usually mainline and linux-next.

In some of the projects I use different ones, e.g. these on tizen.org
(https://review.tizen.org/git/?p=platform/kernel/linux-exynos.git;a=summary).

Best regards,
Krzysztof