1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/fifo_gk20a.c b/drivers/gpu/nvgpu/gk20a/fifo_gk20a.c
index dbed9880..78f777ae 100644
--- a/drivers/gpu/nvgpu/gk20a/fifo_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/fifo_gk20a.c
@@ -2410,6 +2410,34 @@ bool gk20a_fifo_handle_sched_error(struct gk20a *g)
         sched_error = gk20a_readl(g, fifo_intr_sched_error_r());
 
         engine_id = gk20a_fifo_get_failing_engine_data(g, &id, &is_tsg);
+        /*
+         * Could not find the engine
+         * Possible Causes:
+         * a)
+         * On hitting engine reset, h/w drops the ctxsw_status to INVALID in
+         * fifo_engine_status register. Also while the engine is held in reset
+         * h/w passes busy/idle straight through. fifo_engine_status registers
+         * are correct in that there is no context switch outstanding
+         * as the CTXSW is aborted when reset is asserted.
+         * This is just a side effect of how gv100 and earlier versions of
+         * ctxsw_timeout behave.
+         * With gv11b and later, h/w snaps the context at the point of error
+         * so that s/w can see the tsg_id which caused the HW timeout.
+         * b)
+         * If engines are not busy and ctxsw state is valid then intr occurred
+         * in the past and if the ctxsw state has moved on to VALID from LOAD
+         * or SAVE, it means that whatever timed out eventually finished
+         * anyways. The problem with this is that s/w cannot conclude which
+         * context caused the problem as maybe more switches occurred before
+         * intr is handled.
+         */
+        if (engine_id == FIFO_INVAL_ENGINE_ID) {
+                nvgpu_info(g, "fifo sched error: 0x%08x, failed to find engine "
+                                "that is busy doing ctxsw. "
+                                "May be ctxsw already happened", sched_error);
+                ret = false;
+                goto err;
+        }
 
         /* could not find the engine - should never happen */
         if (!gk20a_fifo_is_valid_engine_id(g, engine_id)) {