[RFC,PATCH 0/2] Allow late mdesc detection

[Eric Miao]

On Mon, Jul 12, 2010 at 4:05 PM, Jeremy Kerr <jeremy.kerr at canonical.com> wrote:
> Hi Nicolas,
>
>> The fundamental problem with those patches is that we actually want to
>> move in the opposite direction for the eventual support of multiple SOCs
>> in the same kernel, i.e. rely on the machine ID -> mdesc to determine
>> the right debug addresses at run time and eventually make the addruart
>> into something that is not hardcoded at compile time.
>
> Sure, I think that's where we're going in general, but I think the debug
> stuff is an exception - we want that up as early as possible, and with
> as few dependencies on other bits of code as possible.
>

The debug stuff differs really much from platforms to platforms. My idea
maybe we can leave the early debug part alone, so that when debugging
on a specific platforms, people have to use a non-multi-platform kernel,
and when building a multi-platform kernel, we have to disable the early
debugging mess?

> At present we can only ever select one implementation of addruart in a
> kernel build, so we just can't have a multiplatform kernel with debug
> support. We *could* add other trickery to select a debug implementation
> at runtime, but I think adding complexity to the debug path is a bad
> idea.
>
> I think allowing a hard-coded debug system is fine; it can be enabled
> when we're debugging a specific problem, and removed to enable the true
> multiplatform support. This is also what is done on powerpc - you can
> select a "udbg" output method suitable for your platform at compile
> time, but this doesn't affect the other parts of the kernel.
>
> I also think it's good to only specify the debug parameters in one place
> (addruart), rather than have to provide them in adduart *and* the mdesc.
>
> Thoughts?
>
> Cheers,
>
>
> Jeremy
>
>
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