drm/panfrost: Expose performance counters through unstable ioctls
Expose performance counters through 2 driver specific ioctls: one to enable/disable the perfcnt block, and one to dump the counter values. There are discussions to expose global performance monitors (those counters that can't be retrieved on a per-job basis) in a consistent way, but this is likely to take time to settle on something that works for various HW/users. The ioctls are marked unstable so we can get rid of them when the time comes. We initally went for a debugfs-based interface, but this was making the transition to per-FD address space more complicated (we need to specify the namespace the GPU has to use when dumping the perf counters), hence the decision to switch back to driver specific ioctls which are passed the FD they operate on and thus will have a dedicated address space attached to them. Other than that, the implementation is pretty simple: it basically dumps all counters and copy the values to a userspace buffer. The parsing is left to userspace which has to know the specific layout that's used by the GPU (layout differs on a per-revision basis). Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io> Signed-off-by: Rob Herring <robh@kernel.org> Link: https://patchwork.freedesktop.org/patch/msgid/20190618081648.17297-5-boris.brezillon@collabora.com
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