Am 06.08.20 um 05:46 schrieb Dave Airlie:
That was not what I was talking about. Take a look at what those fields
are used for :)
As far as I see the only usage of the size is in
ttm_resource_manager_debug(). But this size is actually totally opaque
to TTM, it could be pages, bytes, fried chicken wings or whatever. In
other words it would be much better to print it in the debug callback of
each resource manager.
Size is a bit trickier as the drivers use in a couple of funky places, radeon
pokes inside the range manager and adjust its size post init, and amdgpu
uses size to validate a bunch of bo sizing. These shouldn't be too messy to
workaround.
Yeah, I already wanted o clean that up in radeon for years now :)
Amdgpu should be easy to fix, most likely we just don't store the gtt
size anywhere else.
But yes, those are TTM internals which drivers should not touch.
The available_caching is completely superfluous as well. The original
idea what that a driver could specify multiple placements as flags in
one entry, but no driver ever used that as far as I know and it became
completely deprecated in 2014 when I moved the lpfn and fpfn into each
place.
The default_caching is used in ttm_bo_select_caching(), but this is
complete utterly nonsense. It just results in multiple possible cache
behaviors being selected, which are then fortunately ignored by
ttm_tt_set_placement_caching :)
To be honest I think just removing those parameters and the associated
caching flags all together is the next logical step.
Definitely something to burn down alright.
IIRC we have a bit of dead AGP code in radeon which still tries to use this.
Nouveau might have something as well, going to take a look now.
But in general I think that drivers should just say I want caching X for
this BO instead of TTM making an educated guess based on some flags set
in different places.
Christian.
Dave.
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