linux-kernel - Re: [RFC PATCH 0/5] omap: add ocp2scp as a misc driver

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Message-ID: <87fwa01mso.fsf@ti.com>
Date:	Tue, 12 Jun 2012 10:07:35 -0700
From:	Kevin Hilman <khilman@...com>
To:	"ABRAHAM\, KISHON VIJAY" <kishon@...com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	"Cousson\, Benoit" <b-cousson@...com>,
	Paul Walmsley <paul@...an.com>, tony@...mide.com,
	linux@....linux.org.uk, gregkh@...uxfoundation.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, balbi@...com
Subject: Re: [RFC PATCH 0/5] omap: add ocp2scp as a misc driver

"ABRAHAM, KISHON VIJAY" <kishon@...com> writes:

> Hi Kevin, Benoit, Paul,
>
> On Fri, Jun 1, 2012 at 2:16 AM, Arnd Bergmann <arnd@...db.de> wrote:
>> On Thursday 31 May 2012, ABRAHAM, KISHON VIJAY wrote:
>>> > I would mark the multiplexed device compatible with "simple-bus", which
>>> > results in the child devices automatically getting added.
>>>
>>> hmm.. ocp2scp has a sysconfig register and it also has a module mode
>>> by which it can be enabled/disabled. I was making use of pm_runtime
>>> API's to control these registers (Apart from creating child devices,
>>> the driver also has a call to pm_runtime_enable).
>>
>> I see.
>>
>>> I'm not sure if with
>>> "simple-bus" we'll be able to do those. I have to check on that.
>>
>> How about making it compatible with both "simple-bus" and something
>> that handles the pm_runtime requirements?
>>
>> I don't understand enough of what needs to be done for pm_runtime
>> across a lot of devices, but I'd hope that it should be possible
>> to do that in a generic way based on the device definition.
>
> Is there already exists a generic way for handling pm_runtime
> requirements (as simple as doing a pm_runtime_enable on a device).

As you've discovered, the runtime PM core handles the parent/child
relationships already.

> So the actual problem is we have ocp2scp as parent and usb2phy and
> usb3phy as the child device. ocp2scp has the sysconfig register and it
> can be controlled using module mode bit (both of this can be
> controlled by pm_runtime). Whenever usb controller(dwc3/musb) wants to
> enable a phy, it calls an exported API in usb2/usb3 phy to enable it.
> These API's have pm_runtime_get_sync on usb2/usb3 device which in-turn
> calls pm_runtime_get_sync of ocp2scp because of parent->child
> relationship (For this both usb2/usb3 phy and ocp2scp devices should
> have called pm_runtime_enable). All I'm trying is to find a place to
> have pm_runtime_enable for ocp2scp.

Maybe I'm not following, but why can't it be in the driver?

Kevin

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