linux-kernel - Re: [patch 4/4] MFD: Change mfd platform device usage to wrapper platform

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Date:	Wed, 9 Jul 2008 15:34:29 +0200
From:	"pHilipp Zabel" <philipp.zabel@...il.com>
To:	ian <spyro@....com>
Cc:	"Ben Dooks" <ben-linux@...ff.org>, Dmitry <dbaryshkov@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.arm.linux.org.uk
Subject: Re: [patch 4/4] MFD: Change mfd platform device usage to wrapper platform_device

On Wed, Jul 9, 2008 at 3:28 PM, ian <spyro@....com> wrote:
> On Wed, 2008-07-09 at 13:07 +0100, Ben Dooks wrote:
>> > They should be here for exactly the same reason. They are used by
>> the drivers
>> > that will be submitted later. E.g. OHCI driver needs such
>> > suspend/resume handling.
>>
>> No, you don't understand. I'll make a rather explicit point about the
>> very clever way the device tree works since the devices are registered
>> with their parent device set.
>
> Actually I misthought here too.
>
> The problem comes when the subdevices arent *quite* truely independant
> of their core, and thus need to ask the core to turn off power /
> clokcs / etc. for them

I agree "power" and "etc." are issues. Clocks should be handled by the
clock API just fine.

> they cant just do it themselves because the subdevices may be used on
> more than one core that does this hanling in different ways (eg. T7L and
> TC6393XB handle the 32KHz clock completely differently.

That shouln't matter with generic clocks. If they
clk_get(&mfd_cell->pdev.dev, "my_clk_input"), that should be
dispatched to the correct MFD clock regardless of the actual chip.

> on tc6393xb,
> theres a clock gate on the MFD core chip and on t7l66xb the clock has to
> be handled right back at the platform layer, in board specific code
> because the core has no gate, and the clock is fed to it from an
> external pin.

Still, that could be done inside the MFD driver's custom clock
enable/disable methods.

> Thats one example - there are others, not all clocks.
>
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