Benjamin Herrenschmidt wrote: > On Mon, 2009-11-30 at 06:50 +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. >> 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. > > But that doesn't allocate virtual space does it ? >
No. >> See udbg_early_grab_exi_io_base(). > > Yeah, I see that: > > +#if defined(CONFIG_GAMECUBE) > + return (void __iomem *)0x0c006800; > +#elif defined(CONFIG_WII) > + return (void __iomem *)0x0d006800; > +#else > > So you'll have BATs floating over user addresses ? That sounds fishy :-) > Heh, I was told to identity map it :) Originally it used kernel address space (0xc{c,d}006800). > It should be trivial to just create a fixmap entry instead. That will > give you a virtual address that is known at compile time (so you can > use it from head_32.S as well for setting up your BAT). > > Actually you probably need more than one entry in there since it needs > to be big enough to cover a BAT min size and be aligned, but it's not > -that- hard to do (I think x86 does similar tricks in their fixmap > iirc) > I've never worked with fixmap entries. I'll look into it. Thanks. >> 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. > > .../... > >>> You need to allocate the virtual space. For a debug thing like that, you >>> could use the fixmap. In fact, I think we should create a fixmap entry >>> or two always available for use by early debug. >>> >> Or give us back ppc_md.setup_io_mappings :) > > Not happening :-) Or if you get one, it will allocate virtual addresses > and so you cannot rely on an identity mapping. > But we can use then a known mapping scheme, and have all the i/o region covered by bats there. We can do that already, yes, but setup_io_mappings purpose was originally that, no? Thanks, Albert _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev