radeonsi tiling dilema

[Jerome Glisse]

So i am facing a dilema regarding tiling on radeonsi. Given that we now
have a fixed table of tiling mode this put more pressure on the kernel
userspace api. I see either 2 solutions.

Enforce kernel to set at fixed index in the table best tiling mode for
given gpu for given format, such as DEPTH32_2D_4AA at index 4, or
COLOR_SCANOUT_2D at index 13 ... that way kernel can still adapt the tile
mode array value. Note that this match the design behind the tile mode
index being that there is a limited number of useful tile mode combination
and for each surface format  (depth/color/macro tile/micro/tile) there is a
best one.

Second solution is to add an ioctl to compute mipmap information in kernel
(pitch alignment slice size ...) based on format, size of the surface.

Some might argue that we could just export the table content to userspace,
but that would loose information and possibly froze the tile mode table
forever as API. The information we loose is what index match to prefered
surface format/type combination. And the tile mode might be considered API
as if kernel ever change what userspace expect then we might break some
userspace.


Thought, idea ?

Cheers,
Jerome
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