Anyone with MPC82xx PCI on kernel 2.6?
cml3227 at eircom.net
Thu Aug 26 02:41:30 EST 2004
I am trying to bring up a custom board which contains an MPC8250, a
three-port PCI-PCI bridge and a few pci devices. I am using kernel
126.96.36.199. I am having a number of problems.
Currently I have just four devices hanging off one secondary bus of the
pci-pci bridge. Apart from the bridge, I have no other devices hanging
off bus 0. I have nothing yet hanging off bus 2.
| bus 0
|bridge | | bridge |
|device 0x10| |device 0x10|
|function 0 | |function 1 |
|bus 1 |bus 2
| | |
device 1 device 2 device 3
Initially, the bios initialization would not assign resources to my
devices on bus 1. The reason appeared to be that in
pci_read_bridge_bases it reads the memory base and limit registers
from the bridge. As these are initially zero, it sets a limit
of 1MB for the resources assigned to bus 1.
My devices (DSP processors) look for a lot more memory space that that.
I modified the function to assign sufficient resources for my needs
and it now appears to assign memory resources to the devices correctly.
First question: Should the memory limit register be set in the bridge
becore pci_read_bridge_bases? Is it perhaps assumed that the bios (boot
code) sets this up?
I still have an issue with I/O resources that I am ignoring for now.
My primary concern right now is verifying the hardware.
Now I try to access the devices on bus 1. I can read the configuration
space no problem, but get bus error if I read the pci memory space.
Checking everything obvious, I see that the the command register of
the pci-pci bridge does not have the memory or I/O space bits set.
Setting these bits eliminates the bus error.
Second question: What function should set the command register for
the pci-pci bridge to enable access to the secondary bus for
memory and I/O cycles?
Now I am at the stage where I don't get a bus error, but I read all FFs
no matter where I read from bus 1. It doesn't appear to matter if a
device is configured at the address or not.
Next question: What should I look at now? How do I tell if
the device responded to the pci access?
Any help would be much appreciated.
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