gpu: nvgpu: Abstract get_cycles()

get_cycles is a linux specific API used in common code. This API
is being used, it seems, as a method to generate time stamps. So
add an API to generate 'high resolution' time stamps. This API
returns an opaque time stamp: that is not something one may use
directly as a time since in the Linux implementation we just use
this cycle counter.

Other implementations will, of course, be free to implement as a
real time stamp.

JIRA NVGPU-525

Change-Id: I237aac9bd6c795d000459025bdb4fce92e8aaa3d
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1673811
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

3 files changed, 17 insertions, 1 deletions

diff --git a/drivers/gpu/nvgpu/common/bus.c b/drivers/gpu/nvgpu/common/bus.c
index a84348cd..3889512a 100644
--- a/drivers/gpu/nvgpu/common/bus.c
+++ b/drivers/gpu/nvgpu/common/bus.c
@@ -42,7 +42,7 @@ int nvgpu_get_timestamps_zipper(struct gk20a *g,
                 if (err)
                         return err;
 
-                samples[i].cpu_timestamp = (u64)get_cycles();
+                samples[i].cpu_timestamp = nvgpu_hr_timestamp();
         }
 
 end:
diff --git a/drivers/gpu/nvgpu/common/linux/timers.c b/drivers/gpu/nvgpu/common/linux/timers.c
index d0004aa5..41b55543 100644
--- a/drivers/gpu/nvgpu/common/linux/timers.c
+++ b/drivers/gpu/nvgpu/common/linux/timers.c
@@ -241,3 +241,18 @@ s64 nvgpu_current_time_ms(void)
 {
         return ktime_to_ms(ktime_get());
 }
+
+/**
+ * nvgpu_hr_timestamp - Opaque 'high resolution' time stamp.
+ *
+ * Return a "high resolution" time stamp. It does not really matter exactly what
+ * it is, so long as it generally returns unique values and monotonically
+ * increases - wrap around _is_ possible though in a system running for long
+ * enough.
+ *
+ * Note: what high resolution means is system dependent.
+ */
+u64 nvgpu_hr_timestamp(void)
+{
+        return get_cycles();
+}
diff --git a/drivers/gpu/nvgpu/include/nvgpu/timers.h b/drivers/gpu/nvgpu/include/nvgpu/timers.h
index b0df29b6..2e260619 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/timers.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/timers.h
@@ -109,5 +109,6 @@ void nvgpu_udelay(unsigned int usecs);
  * Timekeeping.
  */
 s64 nvgpu_current_time_ms(void);
+u64 nvgpu_hr_timestamp(void);
 
 #endif