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

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Date:	Thu, 31 May 2012 16:48:40 +0530
From:	"ABRAHAM, KISHON VIJAY" <kishon@...com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	paul@...an.com, tony@...mide.com, linux@....linux.org.uk,
	b-cousson@...com, 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

Hi Arnd,

On Thu, May 31, 2012 at 2:52 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Thursday 31 May 2012, ABRAHAM, KISHON VIJAY wrote:
>> >
>> > Just put the devices you actually want into the device tree instead and
>> > have them automatically created.
>>
>> But shouldn't device tree support and non-device tree support co-exist
>> till the non-device tree is completely knocked out of the kernel? Even
>
> Well, it's a new driver, so there is no regression in supporting it only
> on DT-enabled boards. OMAP5 is DT-only anyway and OMAP4 only supports two
> boards that should both be working with the generic DT code already.
>
>> then shouldn't there be a separate driver to extract the child nodes
>> of ocp2scp and create a device (using of_platform_populate)?
>> As far as I've seen, the devices are automatically created (by virtue
>> of of_platform_populate() in  mach-omap2/board-generic.c in omap case)
>> only for the devices that is connected to the system bus. For other
>> cases, the parent should be responsible for creating the child
>> devices.
>
> 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'm not sure if with
"simple-bus" we'll be able to do those. I have to check on that.

Thanks
Kishon
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