PCI DMA memory problem

Chris Zimman chris at cryptoapps.com
Wed Jun 25 05:19:35 EST 2003

On Tue, Jun 24, 2003 at 09:01:21PM +0200, Oliver Amft wrote:
> I am implementing a network driver for a DMA device on a custom
> 405GP/GPr based board. The networking device is attached over PCI bus.
> Kernel is currently 2.4.21. BIOS is PPCBoot 1.2.0.
> 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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