etnaviv: add support for sharing the TS buffer
This adds support for sharing the TS buffer, which up until now has been
an internal implementation detail, with the outside world. This mainly
improves performance with a GPU compositor present, but on i.MX8M also
direct to display use-cases benefit.
The impact of this change depends on the GPU generation:
- old GPUs with a single pipe won't see any difference
- GC2000 can skip the TS resolve in the client and will benefit from a
more efficient blit into the sampler compatible format when the client
buffer contains cleared tiles
- GC3000 can directly sample with TS support, so saves both write and read
memory bandwidth when the client buffer contains cleared tiles
- GC7000 with compression support can keep the client buffer in compressed
format, thus saving both read and write bandwidth even for fully filled
client buffers
- GC7000 coupled to a display unit supporting the compression format (DCSS
on i.MX8M) does not even need to uncompress the render buffer for display
so will see significant bandwidth saving even when GPU compositing is
bypassed
There is a slight complication in that the tile clear color isn't part of
the TS buffer, but is programmed into state registers in the GPU. To handle
this externally shared TS buffers now contain a software metadata area,
where the clear color is stored by the driver, so the receiving end of the
TS buffer can retrieve the clear color from this area.
The compression format is handled in the same way by storing it in the SW
meta area. While we can derive the compression format from the color buffer
format in most cases, some users, like weston, expect that they can "upgrade"
ARGB to XRGB color formats. While this works with plain color formats, as
it's just masking a channel, the compression format differs when alpha is in
use. Receivers of the TS buffer should thus not try to infer the compression
format from the color buffer format, but instead fetch it from the SW meta.
The import/export handling of the TS buffer is modelled after the Intel iris
driver: we add a separate plane for the TS buffer and fold it into the base
resource after the import.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Tested-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9780>
9 files changed
