ioremap() on ISA memory space

[Geert Uytterhoeven]

On Wed, 9 Jun 1999, Geert Uytterhoeven wrote:
> On Tue, 8 Jun 1999, Gabriel Paubert wrote:
> > On Tue, 8 Jun 1999, Geert Uytterhoeven wrote:
> > > I found one reason why current kernels don't work on my LongTrail: my NVRAM is
> > > in ISA memory space. When the kernel tries to ioremap() it in
> > > pmac_nvram_init(), I get
> > > 
> > >     __ioremap(): phys addr e0000 is RAM lr c000e43c
> > > 
> > > and ioremap() returns NULL, causing all later accesses to NVRAM (e.g. in atyfb)
> > > to fail due to NULL pointer dereferences.
> > > 
> > > Do all CHRP boxes have NVRAM in ISA memory space? The comment (by Corey) near
> > > the call to pmac_nvram_init() in chrp_init2() already wonders whether
> > > pmac_nvram_init() should be called or not.
> > 
> > I don't know, but according to M.Mares (the PCI guy), all addresses passed
> > to ioremap should be processor physical addresses. So you should modify
> > the call to ioremap to add the physical offset at which the ISA memory
> > space (address 0-16 Mb) appears on the PCI bus. 
> 
> Oops, you're right (in my case that's an offset of 0xf7000000). Hence we have
> to `fix up' the OF device tree first...

`nvram' is actually `/pci/isa at 1/nvram at me0000' (note the `m' after the `@'), so
the device tree does know it's ISA _memory_ space. But this isn't reflected in
the properties of the node:

| reg                      00000000 000e0000 00008000
| device_type              nvram
| name                     nvram

Well, since the call to ioremap() is protected by a test for CHRP:

        if (_machine == _MACH_chrp && nvram_naddrs == 1) {
                nvram_data = ioremap(dp->addrs[0].address, dp->addrs[0].size);
                nvram_mult = 1;
        } else ...

I think it's safe to always add the ISA memory base offset there.

Greetings,

						Geert

--
Geert Uytterhoeven                     Geert.Uytterhoeven at cs.kuleuven.ac.be
Wavelets, Linux/{m68k~Amiga,PPC~CHRP}  http://www.cs.kuleuven.ac.be/~geert/
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium


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