Subject: Re: [RFC PATCH v2 08/11] powerpc: gamecube/wii: early debugging using usbgecko

From: Albert Herranz <[email-masked]>
Date: Mon, 30 Nov 2009 07:15:42 +0100

Albert Herranz wrote:
> Benjamin Herrenschmidt wrote:
>> On Sat, 2009-11-28 at 21:43 +0100, Albert Herranz wrote:
>>> +        * Prepare again the same BAT for MMU_init.
>>> +        * This allows udbg I/O to continue working after the MMU is
>>> +        * turned on for real.
>>> +        *
>>> +        * We are assuming here that exi_io_base is identity mapped.
>>> +        */
>>> +       addr = ((unsigned long)exi_io_base) & 0xffff0000;
>>> +       setbat(1, addr, addr, 128*1024, PAGE_KERNEL_NCG); 
>> How do you prevent that from overlapping otherwise valid kernel
>> mappings ?
>>
> 
> ug_udbg_init() is called from ppc_md.init_early.

  ^^^
This got here, but although it's true it doesn't apply here :)

> It doesn't overlap any valid kernel mappings because exi_io_base is hardcoded to an i/o region not used yet by the kernel.
> See udbg_early_grab_exi_io_base().
> The setbat just prepares again, exactly in the same way, the same BAT that we got setup by setup_usbgecko_bat in head_32.S.
> 

Thanks,
Albert