Subject: Re: PCI on 834x

From: Scott Wood <[email-masked]>
Date: Thu, 25 Feb 2010 15:24:51 -0600

Gary Thomas wrote:
> On 02/25/2010 02:03 PM, Scott Wood wrote:
>> Gary, can you check that the MMIO addresses are going to the PCI bus 
>> as-is, and aren't being translated down to zero? I.e. POTARn should 
>> equal POBARn, and likewise in the device
>> tree's pci node's ranges.
> 
> Hmm, that doesn't match with how I've always had this setup.  I have:
>   POTAR0 = 0x00000000
>   POTBR0 = 0x000C0000        (0xC0000000 >> 12)
> 
> My device tree mappings are:
>   ranges = <0x02000000 0x0 0xC0000000 0xC0000000 0x0 0x10000000
>             0x01000000 0x0 0x00000000 0xB8000000 0x0 0x00100000>

That ranges property says that host address 0xc0000000 maps to PCI 
address 0xc0000000, so Linux will program the BAR to 0xc0000000, but the 
actual accesses will go elsewhere because POTAR0 is zero.

Setting POTAR to zero is also a bad idea because it's aliasing your DMA 
window (it may work in certain situations based on who's initiating the 
transaction, but it seems like it's asking for trouble), plus it seems 
some cards just don't like address zero.

Try setting POTAR0 to 0x000c0000 and see what happens.

-Scott