The DMA region must be accessible in order for PCI peripheral
drivers to work, the sparc32 has DMA in the normal memory
zone which requires the GRPCI2 to PCI target BARs so that all
kernel low mem (192MB) can be mapped 1:1 to PCI address
space. The GRPCI2 has resizeable target BARs, by default the
first is made 256MB and all other BARs are disabled.

I/O space are always located on 0x1000-0x10000, but accessed
through the GRPCI2 PCI I/O Window memory mapped to virtual
address space.

Configuration space is accessed through the 64KB GRPCI2 PCI
CFG Window using LDA bypassing the MMU.

The GRPCI2 has a single PCI Window for prefetchable and non-
prefetchable address space, it is up to the AHB master
requesting PCI data to determine access type. Memory space
is mapped 1:1.

The GRPCI2 core can be configured in 4 different IRQ modes,
where PCI Interrupt, Error Interrupt and DMA Interrupt are
shared on a single IRQ line or at most 5 IRQs are used. The
GRPCI2 can mask/unmask PCI interrupts, Err and DMA in the control
and check status bits which tells us which IRQ really happended.
The GENIRQ layer is used to unmask/mask each individual IRQ
source by creating virtual IRQs and implementing a IRQ chip.

The optional DMA functionality of the GRPCI2 is not supported
by this patch.
Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>