[PATCH v2 8/9] ARM: dts: refresh dts file for arch mmp

[Haojian Zhuang]

On Wed, Jun 6, 2012 at 9:47 AM, Mitch Bradley <wmb at firmworks.com> wrote:
> On 6/5/2012 3:28 PM, Arnd Bergmann wrote:
>>
>> On Tuesday 05 June 2012, Chris Ball wrote:
>>>
>>> Hi Haojian,
>>>
>>> On Fri, May 04 2012, Haojian Zhuang wrote:
>>>>
>>>> Append mmp2 and pxa910 dts files. Update PXA168 dts files for irq,
>>>> timer, gpio components.
>>>
>>>
>>> The patch I'm replying to introduced a device tree for MMP2/Brownstone
>>> in 3.5-rc1.  We're looking at adopting the MMP2 device tree for the OLPC
>>> XO-1.75 board, and Mitch Bradley has some corrections to the device tree
>>> format that we'd like to make, appended below.
>>>
>>> You can see all of the files Mitch mentions at:
>>> http://dev.laptop.org/~wmb/mmp2-devicetree/
>>>
>>> Here's my proposal for what to do next:
>>>  * First, you choose one of the two forms that Mitch links to.
>>>    (Either "mmp2.dtsi" or "mmp2-flat.dtsi"; we have a weak preference
>>>    for mmp2-flat.dtsi.)
>>
>>
>> My preference would be towards mmp2.dtsi. I've recommended doing it
>> that way to other people, too.
>
> In most cases, I have found that exposing the full hierarchy is preferable.
>  For this specific SoC, which I have been working with for quite awhile now,
> I haven't found any instance where exposing the AXI/APB levels buys you
> anything.  The hierarchy just adds clutter.
>
> That said, I don't feel strongly about it.
>
mmp2-brownstone.dts is too complex since both apb & axi are imported.
Could we only use flat structure in mmp2-brownstone.dts?

>
>>
>>
>>> d) Moved the "intcmux" nodes down a level so they are children of the
>>> top-level interrupt-controller node.  The problem with having them as
>>> peers of the top-level interrupt-controller is that their "reg"
>>> properties conflict.  For example:
>>> intcmux4 at d4282150 { ... reg =<0x150 0x4>,<0x168 0x4>  ... }
>>>
>>> This is incorrect in several ways:
>>>
>>>    1) "@d4282150" is inconsistent with "reg =<0x150" .  The "unit
>>>       address" after @ is supposed to be the same as the first component
>>>       of the reg property.  d4282150 is not identical to 150.
>>
>>
>> I thought the rule was that the @... part should be a translated address
>> in the presence of "ranges" translation so we get a unique value in case
>> we have multiple devices of the same name on the same address but on
>> different buses.
>>
>> If we change this here, I suppose it also needs to be changed in a number
>> of other places, and we have to rethink the method for unique device
>> names.
>
>
> My thinking was that "ranges" is inappropriate in this case (within the
> top-level interrupt controller node), and I got rid of it.  That being the
> case, this is not "in the presence of ranges".
>
>
>>
>>
>>> The solution is to put the intcmux nodes underneath the
>>> interrupt-controller node.  The interrupt-controller node now has
>>> #address-cells and #size-cells properties so it can have children, but
>>> it does not have a ranges property, so the address space is not passed
>>> through.  The child (intcmux) reg addresses can then be interpreted
>>> independently, without conflict.
>>
>>
>> Right. The implication for this however is that the driver cannot
>> treat the reg property as a physical address it can do ioremap on,
>> but needs to interface with the driver that provides the address
>> space.
>
>
> Indeed.  For this driver, the intcmux subnodes are handled by the same
> driver as the top-level interrupt controller, and those subordinate
> registers are accessed via that driver's one mapping of the register block.
>
Mitch,

Did you test cascade intcmux in DTS? I tried it before and got failure. But I
didn't dig it yet, so I use parallel intc node instead.