[PATCH] drm/radeon: insist on 32-bit DMA for Cedar on PPC64/PPC64LE

[Christian König]

Am 22.02.2018 um 18:56 schrieb Michel Dänzer:
> On 2018-02-22 06:37 PM, Ben Crocker wrote:
>> One of my colleagues did discover a "Radeon HG 5450 PCI" from February
>> 2010 which did, apparently, have a Cedar GPU and very definitely had a
>> (plain old) PCI connector.
> There must be a PCIe-to-PCI bridge on that board. The GPU itself is
> always PCIe, and treated accordingly by the driver.

Ben, just an educated guess but is this one the one which is failing to 
work correctly?

Cause the PCIe bus interface is pretty much identical over all 
generations of the last decade or so. Only the newest Vega10 generation 
is a bit different.

So I strongly thing that this isn't related to the device being a Cedar 
at all, but rather that you have a bridge above it which doesn't 
correctly handle 64bit transfers.

Can you please send and "lspci -t" of both the working and the 
problematic devices?

Thanks,
Christian.