On 5/30/19 2:03 AM, Alexey Kardashevskiy wrote:

This is an attempt to allow DMA masks between 32..59 which are not large
enough to use either a PHB3 bypass mode or a sketchy bypass. Depending
on the max order, up to 40 is usually available.


This is based on v5.2-rc2.

Please comment. Thanks.

I have tested this patch set with an AMD GPU that's limited to <64bit
DMA (I believe it's 40 or 42 bit). It successfully allows the card to
operate without falling back to 32-bit DMA mode as it does without
the patches.

Relevant kernel log message:

[    0.311211] pci 0033:01     : [PE# 00] Enabling 64-bit DMA bypass

Tested-by: Shawn Anastasio <redacted>