In message 000101c61b7e$5c942600$d901a8c0@SN8032 you wrote:

I'm using on my custom board (PPC 440GX) an ATI M6-C16H Mobility Radeon video card. I work with U-boot 1.1.2. I can access the configuration space of ATI with the functions: pci_read_config_dword(..) and pci_write_config_dword(.)

You can also test this using simple "md" and "mw" commands.

Now I have to access the memory space of the ATI. I use the functions: readl(.) and writel(..)

But when I start u-boot, it hangs. I can not access the memory base address of the ATI.

This is more or less to be expected.

Can someone please give me information how U-Boot handles with PCI devices when accessing the memory space.

This has nothing to do with U-Boot or PCI accesses. Your problem is most probably that the ATI graphics card expects that it's memory controller gets initialized - which is normally done by the (x86) BIOS code of the card. Without such initialization you simply cannot access the RAM on the card - which is what's causing your hang -- exactly like your system will hang if you try to access the on-board DRAm without proper initialization.

Best regards,

Wolfgang Denk