Problems with PCI on 8280

Scott Wood scottwood at
Fri Jan 18 10:18:32 EST 2008

Rune Torgersen wrote:
>  >From: Scott Wood
>  >Are you using cuImage, or a regular uImage with a device-tree-aware u-boot
> cuImage for now.
>  >If the former, try commenting out the call to fixup_pci() in
>  >arch/powerpc/boot/cuboot-pq2.c and let me know if that changes anything.
> Did that, That made our PCI bus fail completely

Hmm...  that suggests that something in u-boot's setup is either 
incorrect, or (more likely in this case) doesn't match the device tree.

Or maybe it's the bus parking/arbiter tweaking at the end that u-boot is 

> We have our PCI set up to ONE 512MB outbound range doing all three.
> (I can see where you'd save on mem usage by doing two)
> I do see a bug tho.
> In our case prefetch is 256MB, memio is 128MB.
> the calculation for outbound wiondow 1 sets the size to ~(pref+mmio-1). 
> That only works if the resulting size is a power of 2.

Ah.  Yes, I was assuming both windows would be the same size.  The code 
should be changed to check that, and if any conditions for setting 
PCIBRx/PCIMSKx fail, check to see if the firmware-provided values work 
(and if not, bail without touching anything).

> If we comment out the rewrite of the outbound windows, we get PCI to work.
> But since our u-boot sets everything up correctly (Including prefecable 
> memory) we should not need this? or is it rewriting the device tree in 
> some way?

You shouldn't need it...  I'd compare the register values u-boot sets 
with the values the corrected fixup_pci() sets (including the soc regs 
at the end).  Something must be different.

There is no device tree re-writing; it tries to program the hardware to 
match what's in the device tree.


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