Subject: Re: [PATCH] PowerPC: Remove hardcoded BAT configuration of IMMR in CPM early debug console

From: Martyn Welch <[email-masked]>
Date: Thu, 03 Jun 2010 10:12:19 +0100

Scott Wood wrote:
> On 06/02/2010 03:06 AM, Martyn Welch wrote:
>>>>> I think that's a more fundamental change to CPM early debug than I
>>>>> can
>>>>> handle right now.
>>>
>>> Is IMMRBASE on your board at some address that has a low likelihood of
>>> conflicting when treated as a kernel effective address?
>>
>> It's at 0x0f000000, is seems ok, but then I'm not sure I fully
>> understand kernel effective addresses.
>
> That overlaps userspace -- is the BAT cleared before userspace starts?
>

To be honest, once I'd got the device booting past the early debug
stage, I rebuilt the kernel without udbg in it...

> If you don't want to do the fixmap stuff, might want to at least just
> leave it at the current arbitrary effective address, which hasn't
> seemed to cause much trouble so far.
>

Given that I've now switched udbg off in the kernel config, I really
can't substantiate spending much more time on this. This patch was
mainly to help others that maybe struggling to bring up Linux on a
device with CPM serial.

I'll try and get a revised patch out soon which keeps the current
arbitrary effective address.

Martyn

> But fixmap is the right way to do it.
>
> -Scott

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