PCI DMA memory problem

Oliver Amft oam at gmx.net
Thu Jun 26 22:36:22 EST 2003

The problem was a wrong PCI configuration of the 405 with two colliding
PCI target mappings (PTM1 and PTM2).


>> To map the data buffers from skb the driver uses pci_map_single().
>> When starting the kernel with SDRAM size configurations other
>> than 32MByte the device is unable to transfer data (currupted
>> data) - descriptor dword read/write-back works (set up with
>> pci_alloc_consistent()). For the kernel start option mem=32MB
>> everything is fine (descriptor + correct data).
> My first thought is -- is/are the SDRAM bank(s) configured correctly?
> I don't know that it'd necessarily be related, but for the 405GP,
> PPCBoot 1.2.0 doesn't have the PCI bridge setup quite right for all
> PCI devices (eg. 82559 won't work). I have code to fix the bridge
> setup if you need it -- although I'm not even certain they exist in
> the GPR.

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