On 11/29/2010 11:24 AM, tiejun.chen wrote: > Wolfgang Grandegger wrote: >> Hello, >> >> 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: [44] 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. > > Tiejun > >> >> TIA, >> >> Wolfgang. >> >> > > >
