On Fri, May 12, 2023 at 07:12:21PM +0100, Robin Murphy wrote: > On 2023-05-12 17:49, Jason Gunthorpe wrote: > > On Fri, May 12, 2023 at 05:55:23AM +0300, Dmitry Osipenko wrote: > > > > > > > This has occasionally come up in the past and I seem to remember that it > > > > > had once been proposed to simply remove tegra-gart and there had been no > > > > > objections. Adding Dmitry, if he doesn't have objections to remaving it, > > > > > neither do I. > > > > > > > > Dmitry, please say yes and I will remove it instead of trying to carry > > > > it. The driver is almost 10 years old at this point, I'm skeptical > > > > anyone will need it on a 6.2 era kernel.. > > > > > > You probably missed that support for many of 10 years old Tegra2/3 > > > devices was added to kernel during last years. > > > > > > This GART isn't used by upstream DRM driver, but it's used by downstream > > > kernel which uses alternative Tegra DRM driver that works better for > > > older hardware. > > > > It is kernel policy not to carry code to only support out of tree drivers in > > mainline, so it should be removed, thanks > > Aww, I was literally in the middle of writing a Friday-afternoon patch to > fix it... still need to build-test, but it's really not looking too bad at > all: But we still need some kind of core support to accommodate a domain with a mixture of identity and translation. Seems a bit pointless for a driver with no in tree user even? > After that I was going to clean up the force_aperture confusion. Oh I already made a patch to delete it :) > TBH I've grown to rather like having this driver around as an > exception to prove our abstractions and help make sure they make > sense Except nobody else seems to know it is here or really understand how weird/broken it is compared to the other drivers. We've managed to ignore the issues, but I wouldn't say it is helping build abstractions. If we remove this driver then the iommu subsystem has no HW with a mixed translation in the iommu_domain and looking forwards I think that will be the kind of HW people want to build. The remaining GART-like hardware is in arch code. > not like there aren't plenty of in-tree drivers for hardware even > more ancient, obscure and less-used than Tegra20. FWIW I have > *20*-year-old hardware at home running an up-to-date mainline-based > distro for a practical purpose, but I guess that's considered valid > if it says Intel on it? :P Well, We keep trying to remove stuff across the kernel.. This week I heard about removing areas of HIGHMEM support, removing ia64 and even some rumbles that it is time to say good bye to ia32 - apparently it is now slightly broken. Who knows what will stick in the end but it is not just ARM. Stuff tends to get removed when it stands in the way.. On the other hand stuff with no in-tree user should just be summarily deleted. We have enough problems keeping actual ancient used code going, the community doesn't need even more work to support some out of tree stuff. Jason
