Wolfgang Grandegger wrote:
> I'm trying to read from mmapped PCI memory space on an alchemy board,
> but I can't get it to work. Here's the lspci output of the PCI card:
> bash-3.00# lspci -v
> 00:00.0 Class 0200: 168c:001b (rev 01)
> Subsystem: 168c:2063
> Flags: bus master, medium devsel, latency 168, IRQ 9
> Memory at 0000000040000000 (32-bit, non-prefetchable) [size=64K]
> Capabilities:  Power Management version 2
> I used mmap on "/dev/mem" and "/sys/bus/pci/.../resource0", but I do not
> read the expected values using "*(volatile u32 *)mmap_addr" from that
> region. The value also changes from read to read. Reading from kernel
> space just work fine. Am I doing something illegal? Any idea why it does
> not work?
Form here I'm not sure how you did exactly.
Theoretically, you can mmap() directly that at least from the sys resource. But
I think you have to notice the aligning requirement for a page. I means you
should firstly map one given base_address & ~(PAGE_SIZE - 1). Then access the
last destination address with adding the corresponding offset as you want.
Hope its useful.