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Message-ID: <1d6f2ceb8d3538c906a1fdb8cd3d4c74ccffa42e.camel@kernel.crashing.org>
Subject: Re: [PATCH] arm64: Enable PCI write-combine resources under sysfs
From:   Benjamin Herrenschmidt <benh@kernel.crashing.org>
To:     Jason Gunthorpe <jgg@nvidia.com>, Clint Sbisa <csbisa@amazon.com>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        linux-pci@vger.kernel.org, Bjorn Helgaas <helgaas@kernel.org>,
        linux-arm-kernel@lists.infradead.org, will@kernel.org,
        catalin.marinas@arm.com, Leon Romanovsky <leon@kernel.org>
Date:   Tue, 15 Sep 2020 08:00:27 +1000
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On Tue, 2020-09-15 at 07:42 +1000, Benjamin Herrenschmidt wrote:
> 
> > which is back to my original question, how do you do DMA using
> > /sys/xx/resources? Why not use VFIO like everything else?
> 
> Note: All this doesnt' change the fact that sys/xx/resources_wc
> exists
> for other archs and I see no reasons so far not to have it on ARM...

Also... it looks like VFIO also doesn't provide a way to do WC yet
unfortunately :-(

There was a discussion 2 or 3 years ago while I was at IBM about ways
to add that functionality, but it doesn't seem to have resulted in
anything.

Cheers,
Ben.