Re: [PATCH] drm/i915/perf: Configure OAR controls for specific context

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On Fri, Nov 08, 2019 at 09:22:00AM +0200, Lionel Landwerlin wrote:
On 08/11/2019 01:34, Umesh Nerlige Ramappa wrote:
It turns out that the OAR CONTROL register is not getting configured
correctly in conjunction with the context save/restore bit. When
measuring work for a single context, the OAR counters do not increment.

- Configure OAR format and enable OAR counters at the same time as
  enabling context save/restore for OAR counters.
- Make SAMPLE_OA_REPORT optional from gen12.

v2: Update commit message

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_perf.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 2c380aba1ce9..527a16637689 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -2219,26 +2219,33 @@ static int gen8_configure_context(struct i915_gem_context *ctx,
 	return err;
 }
-static int gen12_emit_oar_config(struct intel_context *ce, bool enable)
+static int gen12_emit_oar_config(struct i915_perf_stream *stream, bool enable)
 {
 	struct i915_request *rq;
+	struct intel_context *ce = stream->pinned_ctx;
 	u32 *cs;
+	u32 format = stream->oa_buffer.format;
 	int err = 0;
 	rq = i915_request_create(ce);
 	if (IS_ERR(rq))
 		return PTR_ERR(rq);
-	cs = intel_ring_begin(rq, 4);
+	cs = intel_ring_begin(rq, 6);
 	if (IS_ERR(cs)) {
 		err = PTR_ERR(cs);
 		goto out;
 	}
-	*cs++ = MI_LOAD_REGISTER_IMM(1);
+	*cs++ = MI_LOAD_REGISTER_IMM(2);
+	/* Enable context save/restore of OAR counters */
 	*cs++ = i915_mmio_reg_offset(RING_CONTEXT_CONTROL(ce->engine->mmio_base));
 	*cs++ = _MASKED_FIELD(GEN12_CTX_CTRL_OAR_CONTEXT_ENABLE,
 			      enable ? GEN12_CTX_CTRL_OAR_CONTEXT_ENABLE : 0);
+	/* Enable OAR counters */
+	*cs++ = i915_mmio_reg_offset(GEN12_OAR_OACONTROL);
+	*cs++ = (format << GEN12_OAR_OACONTROL_COUNTER_FORMAT_SHIFT) |
+		(enable ? GEN12_OAR_OACONTROL_COUNTER_ENABLE : 0);
 	*cs++ = MI_NOOP;


It's probably a good idea to configure OAR in this function indeed :)


But we're already supposed to program it through context image modification in lrc_configure_all_contexts().

So it probably means we have the wrong offset?


We should probably remove it from lrc_configure_all_contexts() then. It's probably trashing some other bit of the context image.


Offset is correct.

When I removed the configuration from lrc_configure_all_contexts(), the test broke :( Debugging further, it looks like OAR config (OAR_OACONTROL and RING_CONTEXT_CONTROL) must be applied to pinned ctx image as well as with LRI using kernel_context

For gen12, lrc_configure_all_contexts only needs to configure the stable power state.

Posting rev2, verified with test as posted here - https://patchwork.freedesktop.org/patch/339514/?series=69164&rev=1 The expectation is that oar counters are saved and restored only for the context passed in perf open ioctl. Also, if some other context issues MI_RPC, it should get valid timestamps, context id etc.., but zeroed counter reports. Let me know if this is not the right understanding.


 	intel_ring_advance(rq, cs);
@@ -2474,8 +2481,7 @@ static int gen12_enable_metric_set(struct i915_perf_stream *stream)
 	 * requested this.
 	 */
 	if (stream->ctx) {
-		ret = gen12_emit_oar_config(stream->pinned_ctx,
-					    oa_config != NULL);
+		ret = gen12_emit_oar_config(stream, oa_config != NULL);
 		if (ret)
 			return ret;
 	}
@@ -2513,7 +2519,7 @@ static void gen12_disable_metric_set(struct i915_perf_stream *stream)
 	/* disable the context save/restore or OAR counters */
 	if (stream->ctx)
-		gen12_emit_oar_config(stream->pinned_ctx, false);
+		gen12_emit_oar_config(stream, false);
 	/* Make sure we disable noa to save power. */
 	intel_uncore_rmw(uncore, RPM_CONFIG1, GEN10_GT_NOA_ENABLE, 0);
@@ -2713,7 +2719,8 @@ 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)) {


Good point, but this should probably go into another patch.

Note that we could also consider not sampling the OA buffer a non privileged operation on Gen12+, since the counters are per context saved/restored.


The TGL support patch already makes 'not sampling the OA buffer' non-privileged. These changes are only clearing the path. I have moved them to a separate patch in v2.

Thanks,
Umesh


Thanks,


-Lionel

 		DRM_DEBUG("Only OA report sampling supported\n");
 		return -EINVAL;
 	}
@@ -2745,7 +2752,7 @@ 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;


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