Nouveau - Jul 2018 - [RFC PATCH v1 0/6] Resolve unwanted DMA backing with IOMMU

On Fri, Jul 27, 2018 at 05:10:22PM +0300, Dmitry Osipenko
wrote:
> I'm not sure what you guys are meaning by the "firmware",
could you elaborate
> please? Do you mean the Open Firmware and hence the devicetree or what?
Yes, I think the best way to request this is using a device-tree
property. Letting the device driver request it is definitly a bad idea.


	Joerg

On Fri, Jul 27, 2018 at 8:20 AM Joerg Roedel <joro at 8bytes.org>
wrote:
>
> On Fri, Jul 27, 2018 at 05:10:22PM +0300, Dmitry Osipenko wrote:
> > I'm not sure what you guys are meaning by the
"firmware", could you elaborate
> > please? Do you mean the Open Firmware and hence the devicetree or
what?
>
> Yes, I think the best way to request this is using a device-tree
> property. Letting the device driver request it is definitly a bad idea.
I don't follow why we need a property rather than being implied by the
device's (the GPU) compatible string.

Rob

On Fri, Jul 27, 2018 at 11:13:31AM -0600, Rob Herring
wrote:
> I don't follow why we need a property rather than being implied by the
> device's (the GPU) compatible string.
There might be devices where either setup works, with or without IOMMU
translation, and the firmware can set the property depending on whether
the user wants more performance or more security.

If we have a whitelist in the kernel this gets more complicated, we
probably need additional kernel-parameters to overwrite those whitelist
entries. Having a property in the device-tree seems to be a better way
here, imho.


	Joerg