gpu: nvgpu: fix trace ring read after invalid entry

gk20a_fecs_trace_poll() right now calls gk20a_fecs_trace_ring_read()
to read the trace ring buffer written by FECS
gk20a_fecs_trace_ring_read() returns number of trace entries written
to local buffer if successful, otherwise returns error

In case there is really an invalid entry, gk20a_fecs_trace_poll()
will just stop reading more entries, write current read pointer to
h/w and return

When gk20a_fecs_trace_poll() is called next time, we again read that
invalid entry, and again skip it, and again return
This keeps happening, and we never move on to read new entries

Fix this by always continuing to read next entry irrespective
of current entry is valid or not
gk20a_fecs_trace_poll() now just prints a debug message instead of
breaking the loop

Bug 200491708
Bug 200542611

Reviewed-on: https://git-master.nvidia.com/r/2020167
(cherry picked from commit decbbf35041e7e551b3f354e582daaa5c8c3cc0a)

Change-Id: If8b3c8af63ce662a41ada93a6986fa149e34f664
Signed-off-by: seshendra <sgadagottu@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/2190151
GVS: Gerrit_Virtual_Submit
Reviewed-by: Vinod Gopalakrishnakurup <vinodg@nvidia.com>
Reviewed-by: Alex Waterman <alexw@nvidia.com>
Reviewed-by: Winnie Hsu <whsu@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/fecs_trace_gk20a.c b/drivers/gpu/nvgpu/gk20a/fecs_trace_gk20a.c
index ba85e3a3..5c1c5e0e 100644
--- a/drivers/gpu/nvgpu/gk20a/fecs_trace_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/fecs_trace_gk20a.c
@@ -371,8 +371,10 @@ int gk20a_fecs_trace_poll(struct gk20a *g)
 
         while (read != write) {
                 cnt = gk20a_fecs_trace_ring_read(g, read);
-                if (cnt <= 0)
-                        break;
+                if (cnt > 0) {
+                        nvgpu_log(g, gpu_dbg_ctxsw,
+                                "number of trace entries added: %d", cnt);
+                }
 
                 /* Get to next record. */
                 read = (read + 1) & (GK20A_FECS_TRACE_NUM_RECORDS - 1);