gpu: nvgpu: Add support for FECS ctxsw tracing

bug 1648908

This commit adds support for FECS ctxsw tracing. Code is compiled
conditionnaly under CONFIG_GK20_CTXSW_TRACE.
This feature requires an updated FECS ucode that writes one record to a ring
buffer on each context switch. On RM/Kernel side, the GPU driver reads records
from the master ring buffer and generates trace entries into a user-facing
VM ring buffer. For each record in the master ring buffer, RM/Kernel has
to retrieve the vmid+pid of the user process that submitted related work.

Features currently implemented:
- master ring buffer allocation
- debugfs to dump master ring buffer
- FECS record per context switch (with both current and new contexts)
- dedicated device for ctxsw tracing (access to VM ring buffer)
- SOF generation (and access to PTIMER)
- VM ring buffer allocation, and reconfiguration
- enable/disable tracing at user level
- event-based trace filtering
- context_ptr to vmid+pid mapping
- read system call for ctxsw dev
- mmap system call for ctxsw dev (direct access to VM ring buffer)
- poll system call for ctxsw dev
- save/restore register on ELPG/CG6
- separate user ring from FECS ring handling

Features requiring ucode changes:
- enable/disable tracing at FECS level
- actual busy time on engine (bug 1642354)
- master ring buffer threshold interrupt (P1)
- API for GPU to CPU timestamp conversion (P1)
- vmid/pid/uid based filtering (P1)

Change-Id: I8e39c648221ee0fa09d5df8524b03dca83fe24f3
Signed-off-by: Thomas Fleury <tfleury@nvidia.com>
Reviewed-on: http://git-master/r/1022737
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/gpu/nvgpu/Kconfig b/drivers/gpu/nvgpu/Kconfig
index d0e25aa2..94173976 100644
--- a/drivers/gpu/nvgpu/Kconfig
+++ b/drivers/gpu/nvgpu/Kconfig
@@ -54,6 +54,16 @@ config GK20A_CYCLE_STATS
         help
           Say Y here to enable the cycle stats debugging features.
 
+config GK20A_CTXSW_TRACE
+        bool "Support GK20A Context Switch tracing"
+        depends on GK20A
+        default n
+        help
+          Enable support for the GK20A Context Switch Tracing. In this mode,
+          FECS collects timestamps for contexts loaded on GR engine. This
+          allows tracking context switches on GR engine, as well as
+          identifying processes that submitted work.
+
 config TEGRA_GK20A
         bool "Enable the GK20A GPU on Tegra"
         depends on TEGRA_GRHOST || TEGRA_HOST1X