[linux-pm] [PATCH 1/3 v3] ARM: EXYNOS4: Support for generic I/O power domains on EXYNOS4210/4212

[Kukjin Kim]

Chanwoo Choi wrote:
> Hi Kukjin Kim,
> 
> Please reply about Sylwester Nawrocki and me.
> 2011/11/3 Sylwester Nawrocki <s.nawrocki at samsung.com>
> Hi Kgene,
>
> On 11/03/2011 03:09 AM, Kukjin Kim wrote:
> > As I said, I don't think we should control/gate the clocks with
regarding power domain.
> As far as I know there is a plan to let the drivers override
start/stop_device callbacks,
> moreover the clock control can be disabled globally by not implementing
start/stop_device
> callbacks or per device by not adding clkdev entities to the device clock
list at runtime
> PM core. So IMHO, there is/going to be enough flexibility.
>
> > It should be controlled by each regarding device driver and in addition,
as I know,
> > to handle block of clock is not recommended on EXYNOS4 now.
> What do you mean by this ? I couldn't find such information in any
documentation.
> Shouldn't "clock gate block" registers be touched by boot loader and the
kernel?
> Our boot loaders disable all clocks, and if the global clock gate is not
enabled
> by the kernel there is no chance any multimedia device will work.
>
> Should the global clock block gate be always enabled then ? I'm afraid it
is not
> optimal form power management POV.
>
Sylwester, let me check again before replying.

> To Kukjin Kim,
>
Hi Chanwoo,

Firstly, please use text-typed e-mail when you reply.

> > It should be controlled by each regarding device driver and in addition,
as I know,
> > to handle block of clock is not recommended on EXYNOS4 now.
>
> As you said, should we separately control power and clock of power domain?

If you ask my opinion, yes, I mean when it is required, it would be
controlled independent.

> or Have to turn on the clock of power domain always?

I didn't say like that.

> I think that it is to happen unnecessary power consumption.

I don't think, when the power of block/domain is downed, does it happen
_really_ meaningful power consumption?

> If we have to maintain on state of power domain clock, please let me know
guide about this.
>
> Also, 
> For example, fimg2d and framebuffer use LCD0 power domain as parent
device.I
> If fimg2d and framebuffer is disabled state due to not using their,
> I think that we should turn off the clock of LCD0 power domain to reduce
power leakage.

I think, probably it doesn't matter. If any useful data, please let me know.

> Which each regarding device driver control the clock of power domain?
>
> I will expect for your reply.
>

Thanks.

Best regards,
Kgene.
--
Kukjin Kim <kgene.kim at samsung.com>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.