Re: [Intel-gfx] [PATCH 1/2] drm/i915: add gem/gt TODO

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 23 Mar 2021, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> We've discussed a bit how to get the gem/gt team better integrated
> and collaborate more with the wider community and agreed to the
> following:
>
> - all gem/gt patches are reviewed on dri-devel for now. That's
>   overkill, but in the past there was definitely too little of that.
>
> - i915-gem folks are encouraged to cross review core patches from
>   other teams
>
> - big features (especially uapi changes) need to be discussed in an
>   rfc patch that documents the interface and big picture design,
>   before we get lost in the details of the code
>
> - Also a rough TODO (can be refined as we go ofc) to get gem/gt back
>   on track, like we've e.g. done with DAL/DC to get that in shape.

I personally think there should be a lower bar for discussing and
editing the TODO items than via patches on the mailing list. Granted,
the TODO file enforces the discussion happens at a large enough
audience, but for at least some of the items I'd suggest filing gitlab
issues [1], with todo label, and tracking there.

BR,
Jani.


[1] https://gitlab.freedesktop.org/drm/intel/-/issues



>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Jason Ekstrand <jason@jlekstrand.net>
> Cc: Dave Airlie <airlied@redhat.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  drivers/gpu/drm/i915/TODO.txt | 36 +++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>  create mode 100644 drivers/gpu/drm/i915/TODO.txt
>
> diff --git a/drivers/gpu/drm/i915/TODO.txt b/drivers/gpu/drm/i915/TODO.txt
> new file mode 100644
> index 000000000000..d2e5bbb6339d
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/TODO.txt
> @@ -0,0 +1,36 @@
> +gem/gt TODO items
> +-----------------
> +
> +- For discrete memory manager, merge enough dg1 to be able to refactor it to
> +  TTM. Then land pci ids (just in case that turns up an uapi problem). TTM has
> +  improved a lot the past 2 years, there's no reason anymore not to use it.
> +
> +- Come up with a plan what to do with drm/scheduler and how to get there.
> +
> +- There's a lot of complexity added past few years to make relocations faster.
> +  That doesn't make sense given hw and gpu apis moved away from this model years
> +  ago:
> +  1. Land a modern pre-bound uapi like VM_BIND
> +  2. Any complexity added in this area past few years which can't be justified
> +  with VM_BIND using userspace should be removed. Looking at amdgpu dma_resv on
> +  the bo and vm, plus some lru locks is all that needed. No complex rcu,
> +  refcounts, caching, ... on everything.
> +  This is the matching task on the vm side compared to ttm/dma_resv on the
> +  backing storage side.
> +
> +- i915_sw_fence seems to be the main structure for the i915-gem dma_fence model.
> +  How-to-dma_fence is core and drivers really shouldn't build their own world
> +  here, treating everything else as a fixed platform. i915_sw_fence concepts
> +  should be moved to dma_fence, drm/scheduler or atomic commit helpers. Or
> +  removed if dri-devel consensus is that it's not a good idea. Once that's done
> +  maybe even remove it if there's nothing left.
> +
> +Smaller things:
> +- i915_utils.h needs to be moved to the right places.
> +
> +- dma_fence_work should be in drivers/dma-buf
> +
> +- i915_mm.c should be moved to the right places. Some of the helpers also look a
> +  bit fishy:
> +
> +  https://lore.kernel.org/linux-mm/20210301083320.943079-1-hch@lst.de/

-- 
Jani Nikula, Intel Open Source Graphics Center
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