[PATCH 02/20] iommu/terga-gart: Replace set_platform_dma_ops() with IOMMU_DOMAIN_PLATFORM

[Robin Murphy]

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:

  drivers/iommu/tegra-gart.c | 53 +++++++++++++++++-----------------
  1 file changed, 27 insertions(+), 26 deletions(-)

After that I was going to clean up the force_aperture confusion. 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 - it doesn't 
take much effort to keep it functional, and it's 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

Thanks,
Robin.