[issue] Appended device trees does not work for ST-E

[Mounir Bsaibes]

On Fri, Oct 7, 2011 at 2:02 AM, Linus Walleij <linus.walleij at linaro.org>wrote:

> On Thu, Oct 6, 2011 at 6:35 PM, Mounir Bsaibes
> <mounir.bsaibes at linaro.org> wrote:
>
> > issue:
> > "Appended device trees does not work for us. Still don't know why."
>
> I have fixed it now, sorry for all the fuzz, appended device
> trees *are* working for us, as of friday last week.
>
> Excellent - thank you.


> Short story: we're so stupid. (As usual.)
>
> Long story, I *think* core problem was this:
>
> In kernel 3.0 you could enable CONFIG_USE_OF
> and PROC_DEVICETREE to get a dummy device tree in
> /proc/device-tree, so you could enable it just to get the code
> compiled in.
>
> As of 3.1 rc:s if you enable CONFIG_USE_OF, the core
> DT code will start looking for a compatible node, so you
> need a .dt_compat entry in your MACHINE_START
> structure, and it has to reference a matching compat node
> in the device tree. Else it will print an error an hang.
>
> Which is fully logical, if you enable device tree, you should
> use it.
>
> The problem was further complicated that the warning
> about the missing compat node only appears in
> early_printk() context since the console is not up at this
> point, if you don't have that, the machine will hang without
> any prints and you need to figure out what happens.
>
> We enabled early printk:s but since early_printk() is
> problematic with multi-machine configurations we didn't
> see them.
>
> So we were basically hit by the ambigous prossibility to
> configure in earlyprints on machines with the UART in
> different places, which has been discussed by Will Deacon
> et al elsewhere.
>
> Maybe we should document in Kconfig:s
> CONFIG_USE_OF option that if you enable this
> for ARM your machine it won't boot unless it finds a
> compatible device tree, I don't know.
>

copying John Ztultz to handle as he see fit. John is working on kconfig,
maybe he would slip this suggestion in.


>
> Yours,
> Linus Walleij
>



-- 
Mounir Bsaibes
Project Manager

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