[PATCH] ARM: integrator: fix OF-related regression

[Rob Herring]

On Thu, Jun 26, 2014 at 2:39 PM, Rabin Vincent <rabin at rab.in> wrote:
> On Thu, Jun 26, 2014 at 02:15:42PM +0200, Linus Walleij wrote:
>> On Wed, Jun 25, 2014 at 3:06 PM, Rob Herring <robherring2 at gmail.com> wrote:
>> > On Tue, Jun 24, 2014 at 7:08 AM, Linus Walleij <linus.walleij at linaro.org> wrote:
>> >> Commit 07e461cd7e73a84f0e3757932b93cc80976fd749
>> >> "of: Ensure unique names without sacrificing determinism"
>> >> caused a boot failure regression on the Integrator machines.
>> >>
>> >> The problem is probably caused by fiddling too much with
>> >> the device tree population in the OF init function, such
>> >> as passing the SoC bus device as parent when populating
>> >> the device tree.
>> >>
>> >> This patch fixes the problem by:
>> >>
>> >> - Avoiding to explicitly look up the tree root
>> >> - Look up devices needed before device population from
>> >>   the match only, passing NULL as root
>> >> - Passing NULL as root and parent when calling
>> >>   of_platform_populate()
>> >
>> > Just curious, I don't see how this fixes booting for Integrator. Where
>> > exactly does boot fail?
>>
>> It fails by failing to populate the devicetree somehow. I don't
>> have the proper debugging needs, I just trial-and-horror-fixed
>> it by making the board init similar to other platforms :-/
>
> earlyprintk doesn't work on Integrator hardware?  It does on QEMU's
> integratorcp so it's trivial to debug there.

I got as far as building a kernel to do that before getting distracted...

> The problem is that integrator_init_sysfs() adds a device attribute
> called "fpga" to the soc0 bus, and the soc0 bus device is also used as
> the root of the device tree, and the device tree has a node called "fpga".
>
> Before 07e461cd7e73a84f0e3757932b93cc80976fd749 this node directory and
> attribute file had unique paths:
>
>         sysfs: creating file '/devices/soc0/fpga'
>         sysfs: creating dir '/devices/soc0/fpga.0'
>
> 07e461cd7e73a84f0e3757932b93cc80976fd749 removed the .0 from the fpga node's
> directory, leading to that node (and its subnodes) failing to register due to a
> filename conflict with the fpga attribute's file:

Thanks for debugging. Now this makes sense as to why this is specific
to Integrator. I think this is the right direction and we should not
put devices under soc0/. That way the structure is consistent across
SOCs and regardless of whether you decide to create an soc_device or
not.

Rob