On Mon, Sep 03, 2012 at 03:19:13PM +0200, Linus Walleij wrote:

On Mon, Sep 3, 2012 at 2:34 PM, Lee Jones [off-list ref] wrote:

quoted

When booting DT booting take a different path and no platform data
is passed. We can't boot DT AND register devices with platform data
or else we will double probe every device. The only way to pass
pdata when booting with DT is with AUX_DATA() and that's a hack to
get around things we don't have support for yet. Up until now that
has been DMA bindings, clock and pinctrl names and call-backs.

So if we pass some augmented platform data using AUX_DATA()
that appears as pdata in this case, and gets discarded.

Thus we cannot use AUX_DATA() to override a broken, as in
"the interrupt number is wrong" device tree.

No, you cannot to that. You'd have to fix it in DT (which is easier).

quoted

If DT is corrupt or missing the kernel will boot using platform
data, but np will always be NULL, so we don't have the problem you
were alluding to above.

That was not the problem I had in mind.

I had a valid, but incorrect device tree in mind. I.e the device
is there, but with wrong base address, or wrong IRQ number.

If pdata takes precedence, we can use AUX_DATA() to
override such errors from the platform, since drivers/of/platform.c
helpfully pokes in the auxdata as the platform data.

Yes, that's what happens.

I thought this was one of the reasons why auxdata exist
at all.

I don't think so. I've been told that AUXDATA is just a hack. My
aim is to rid the boardfile of all AUXDATA entries.

Or is the proper solution to runtime-patch the device tree
per se in such cases? How is that actually done then?

No, you can't do that either. DT is only read once at boot-time.

The correct solution would be to fix the broken DT.

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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