> On Wed, Apr 01, 2009 at 01:20:49PM -0400, Herrera-Bendezu, Luis wrote:
> >> I am working on a PPC440EPx board with some FPGAs located at
> >> addresses above 4 GB
Cc'ing the PPC list, since they have the most experience with this
CPU, and may have some useful insights. The topic is "UIO on the
PPC440EPx - 36-bit physical addresses".
The PPC440EPx uses 36-bit addressing but is a 32-bit processor.
*All* peripherals are above the first 4 GB - that cannot be changed
if you use this CPU chip.
In general, the solution is to use "struct resource" to carry physical
addresses and sizes. The basic type is:
#ifdef CONFIG_PHYS_ADDR_T_64BIT
typedef u64 phys_addr_t;
#else
typedef u32 phys_addr_t;
#endif
and for this processor, we use u64 rather than u32.
So, if we want to make UIO usable on this class of CPU, we might
replace:
struct uio_mem {
unsigned long addr;
unsigned long size;
int memtype;
void __iomem *internal_addr;
struct uio_map *map;
};
with:
struct uio_mem {
phys_addr_t addr;
phys_addr_t size;
int memtype;
void __iomem *internal_addr;
struct uio_map *map;
};
A few other changes would be needed. We'd have to use something
other than
return sprintf(buf, "0x%lx\n", mem->addr);
because the format would be incorrect for a u64. Also, I believe
we would get warnings in uio_vma_fault(). However, the phys_addr
is really only applicable to UIO_MEM_PHYS, so perhaps we want a
union of phys_addr_t and unsigned long for addr and size?
Anyway, this is a real problem for the PPC440EPx, that board
designers cannot work around.
Steve
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