Am 24.05.2018 um 09:25 schrieb Daniel Vetter:
[SNIP]
Does virtio drm driver need to move buffers around? amdgpu also
has no vram when APU.
Afaiui APUs have a range of stolen memory which looks and acts and is
managed like discrete vram. Including moving buffers around.
BTW: We are actually working on getting rid of that. E.g. the only thing
modern APUs need this stolen VRAM for are page tables, and it's just a
matter of my time to fix this.
From your description you don't have such a requirement, and
then doing what etnaviv has done would be a lot simpler. Everything
that's not related to buffer movement handling is also available
outside of ttm already.
Yeah, I could do like etnaviv, but it's not simpler than using ttm
directly especially want some optimization (like ttm page pool,
ttm_eu_reserve_buffers, ttm_bo_mmap). If I have/want to implement
them, why not just use TTM directly with all those helper functions.
Well TTM has some design flaws (e.g. heavily layered design etc...), but it
also offers some rather nice functionality.
Yeah, but I still think that for non-discrete drivers just moving a
bunch of more of the neat ttm functionality into helpers where
everyone can use them (instead of the binary ttm y/n decision) would
be much better. E.g. the allocator pool definitely sounds like
something gem helpers should be able to do, same for reserving a pile
of buffers or default mmap implementations. A lot of that also exists
already, thanks to lots of efforts from Noralf Tronnes and others.
I think ideally the long-term goal would be to modularize ttm concepts
as much as possible, so that drivers can flexibly pick&choose the bits
they need. We're slowly getting there (but definitely not yet there if
you need to manage discrete vram I think).
Yes, completely agree. It's just that nobody had time for that.
Especially the different memory pools should be cleaned up and moved
into a common DRM functionality or even into the DMA or directly the MM
subsystem.
E.g. an interface like: I'm device X and need memory which is
cached/uncached/wc please allocate something for me.
Regards,
Christian.
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