[U-Boot-Users] PCI access memory space

Wolfgang Denk wd at denx.de
Tue Jan 17 19:10:35 CET 2006

In message <000101c61b7e$5c942600$d901a8c0 at 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

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
When a man sits with a pretty girl for  an  hour,  it  seems  like  a
minute.  But let him sit on a hot stove for a minute -- and it's lon-
ger than any hour. That's relativity.              -- Albert Einstein

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