Subject: [PATCH] cpuidle: kirkwood: Move out of mach directory, add DT.

From: [email-masked] (Rob Herring)
Date: Fri, 28 Dec 2012 08:55:31 -0600

On 12/28/2012 08:35 AM, Andrew Lunn wrote:
> On Fri, Dec 28, 2012 at 08:18:42AM -0600, Rob Herring wrote:
>> On 12/28/2012 06:47 AM, Andrew Lunn wrote:
>>> Move the Kirkwood cpuidle driver out of arch/arm/mach-kirkwood and
>>> into drivers/cpuidle. Convert the driver into a platform driver and
>>> add a device tree binding. Add a DT node to instantiate the driver for
>>> boards converted to DT, and a platform data for old style boards.
>>
>> Is this an old comment? I don't see any platform data.
> 
> There is no platform data, since all the driver needs is an address of
> the DDR control register. The code to create a platform device entry
> is in common.c hunk.

So you should say "a platform device for old style boards".

>>> +		cpuidle at 1418 {
>>> +			compatible = "marvell,kirkwood-cpuidle";
>>> +			reg = <0x1418 0x4>;
>>> +		};
>>> +
>>
>> This is describing what linux wants, not the hardware. This is a common
>> problem with cpuidle drivers in that they use shared registers. I don't
>> have a good solution, but this doesn't belong in DTS.
> 
> Do you have a bad solution?

Ha! :) I should say I don't have a clear, obvious solution.

Don't do a platform driver and just check the machine compatible
property which is what I did for highbank. Have the machine code create
the platform device. Not *all* platform devices have to be created based
on the DTB. Create an MFD driver for the whole block of registers.

> I could just hard code the address, since its the same for all
> kirkwood SoCs. Also, the register is not being used by any other
> code on kirkwood, so its not shared.

Then describe it based on the reference manual, but you need to do so
assuming you are using all the other registers. I assume there are other
registers at say 0x1414 or 0x141c. You have to be careful if you create
separate nodes for each register or sub-group of registers. It needs to
work no matter what the OS expectation is.

Rob