Re: [PATCH 5/6] driver core: lift dma_default_coherent into common code

From: Maciej W. Rozycki
Date: Mon Feb 15 2021 - 08:14:35 EST


On Tue, 9 Feb 2021, Maciej W. Rozycki wrote:

> > > Do you need to have this verified anyhow? I only have a non-coherent 5Kc
> > > Malta though.
> >
> > If you get a chance to test this logic, that would be great.
>
> I'll try to give it a hit in the next few days then. Installed in my
> Malta I have a DEFPA, which is about as serious a DMA user as a piece of
> classic PCI hardware could be. I need to debug the issue of another DEFPA
> not working with my POWER9 system, possibly due to an IOMMU handling bug
> (hopefully not broken host hardware), so I'll take the opportunity and do
> it all at once.

FYI still working on it. The POWER9 issue turned out to be a combination
of a driver configuration issue with the distribution caused by a chain of
historical events leading to the use of PCI I/O bus commands not supported
by the PHB PCIe host bridge and a bad solder joint with the adapter's main
PDQ IC on a 20+ years old brand new card.

I hope to have the adapter properly fixed soon and I'll look at the Malta
side now, possibly using the old server whose DEFPA has worked flawlessly
for some 20 years now. I have planned to use the interface to supply NFS
root, which I think should be enough of a stress test.

Patches will follow sometime too for the driver's configuration issue, a
nonsense in 2021 I should have long addressed, and for resource handling
which I think should explicitly fail port I/O claims on a system that does
not support port I/O at all and should not allow this:

# cat /proc/ioports
00000000-ffffffffffffffff : 0031:02:04.0
#

to happen.

Maciej