drm/i915/perf: Allow non-privileged access when OA buffer is not sampled

SAMPLE_OA_REPORT enables sampling of OA reports from the OA buffer.
Since reports from OA buffer had system wide visibility, collecting
samples from the OA buffer was a privileged operation on previous
platforms. Prior to TGL, it was also necessary to sample the OA buffer
to normalize reports from MI REPORT PERF COUNT.

TGL has a dedicated OAR unit to sample perf reports for a specific
render context. This removes the necessity to sample OA buffer.

- If not sampling the OA buffer, allow non-privileged access. An earlier
  patch allows the non-privilege access:
  https://patchwork.freedesktop.org/patch/337716/?series=68582&rev=1
- Clear up the path for non-privileged access in this patch
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Fixes: 00a7f0d7 ("drm/i915/tgl: Add perf support on TGL")
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191206194339.31356-1-umesh.nerlige.ramappa@intel.com

drivers/gpu/drm/i915/i915_perf.c

@@ -2722,7 +2722,8 @@ static int i915_oa_stream_init(struct i915_perf_stream *stream,
 		return -EINVAL;
 	}
 
-	if (!(props->sample_flags & SAMPLE_OA_REPORT)) {
+	if (!(props->sample_flags & SAMPLE_OA_REPORT) &&
+	    (INTEL_GEN(perf->i915) < 12 || !stream->ctx)) {
 		DRM_DEBUG("Only OA report sampling supported\n");
 		return -EINVAL;
 	}
@@ -2754,7 +2755,7 @@ static int i915_oa_stream_init(struct i915_perf_stream *stream,
 
 	format_size = perf->oa_formats[props->oa_format].size;
 
-	stream->sample_flags |= SAMPLE_OA_REPORT;
+	stream->sample_flags = props->sample_flags;
 	stream->sample_size += format_size;
 
 	stream->oa_buffer.format_size = format_size;