gpu: nvgpu: check engine ctx_status in wait_idle

We have following bug where GPU Host reports non-idle
when it should report engine idle

- if a context is preempted off the GPU, and there is
  no other context to load, NV_PGRAPH_ENGINE_STATUS
  will not be idle until new context is loaded

- this could cause gr_gk20a_wait_idle() to fail since
  here we rely only on NV_PGRAPH_ENGINE_STATUS to
  decide if engine is busy or not

To fix this, first check if context is valid or not
from NV_PFIFO_ENGINE_STATUS_CTX_STATUS

If context is invalid, return immediately
Otherwise, continue as before

Also, add accessors for invalid ctx_status

Bug 1826768

Change-Id: Id627be3f02e79f4beac59a8b5195d08eabf651f2
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/1237521
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/drivers/gpu/nvgpu/gm206/hw_fifo_gm206.h b/drivers/gpu/nvgpu/gm206/hw_fifo_gm206.h
index 56654124..19148b03 100644
--- a/drivers/gpu/nvgpu/gm206/hw_fifo_gm206.h
+++ b/drivers/gpu/nvgpu/gm206/hw_fifo_gm206.h
@@ -426,6 +426,10 @@ static inline u32 fifo_engine_status_ctx_status_v(u32 r)
 {
         return (r >> 13) & 0x7;
 }
+static inline u32 fifo_engine_status_ctx_status_invalid_v(void)
+{
+        return 0x00000000;
+}
 static inline u32 fifo_engine_status_ctx_status_valid_v(void)
 {
         return 0x00000001;