gpu: nvgpu: hold power ref for deterministic channels

To support deterministic channels even with platforms where railgating
is supported, have each deterministic-marked channel hold a power
reference during their lifetime, and skip taking power refs for jobs in
submit path for those.

Previously, railgating blocked deterministic submits in general because
of gk20a_busy()/gk20a_idle() calls in submit path possibly taking time
and more significantly because the gpu may need turning on which takes a
nondeterministic and long amount of time.

As an exception, gk20a_do_idle() can still block deterministic submits
until gk20a_do_unidle() is called. Add a rwsem to guard this. VPR resize
needs do_idle, which conflicts with deterministic channels' requirement
to keep the GPU on. This is documented in the ioctl header now.

Make NVGPU_GPU_FLAGS_SUPPORT_DETERMINISTIC_SUBMIT_NO_JOBTRACKING always
set in the gpu characteristics now that it's supported. The only thing
left now blocking NVGPU_GPU_FLAGS_SUPPORT_DETERMINISTIC_SUBMIT_FULL is
the sync framework.

Make the channel debug dump show which channels are deterministic.

Bug 200291300
Jira NVGPU-70

Change-Id: I47b6f3a8517cd6e4255f6ca2855e3dd912e4f5f3
Signed-off-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-on: http://git-master/r/1483038
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/uapi/linux/nvgpu.h b/include/uapi/linux/nvgpu.h
index e7d37221..00081c64 100644
--- a/include/uapi/linux/nvgpu.h
+++ b/include/uapi/linux/nvgpu.h
@@ -1359,6 +1359,10 @@ struct nvgpu_alloc_gpfifo_ex_args {
 /*
  * Channel shall exhibit deterministic behavior in the submit path.
  *
+ * NOTE: as an exception, VPR resize may still cause the GPU to reset at any
+ * time, which is not deterministic behavior. If this is not acceptable, the
+ * user has to make sure that VPR resize does not occur.
+ *
  * With this flag, any submits with in-kernel job tracking also require that
  * num_inflight_jobs is nonzero, and additionally that
  * NVGPU_GPU_FLAGS_SUPPORT_DETERMINISTIC_SUBMIT_FULL is found in gpu