drm/i915/perf: add missing delay for OA muxes configuration

This was dropped from the original patch series, we weren't sure
whether it was needed at the time. More recent tests show it's
definitely needed to have acurate performance data.
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 19f81df2 ("drm/i915/perf: Add OA unit support for Gen 8+")
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
[ickle: combine duplicate code and comments]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190710105524.23017-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_perf.c

@@ -1569,28 +1569,10 @@ static void config_oa_regs(struct drm_i915_private *dev_priv,
 	}
 }
 
-static int hsw_enable_metric_set(struct i915_perf_stream *stream)
+static void delay_after_mux(void)
 {
-	struct drm_i915_private *dev_priv = stream->dev_priv;
-	const struct i915_oa_config *oa_config = stream->oa_config;
-
-	/* PRM:
-	 *
-	 * OA unit is using “crclk” for its functionality. When trunk
-	 * level clock gating takes place, OA clock would be gated,
-	 * unable to count the events from non-render clock domain.
-	 * Render clock gating must be disabled when OA is enabled to
-	 * count the events from non-render domain. Unit level clock
-	 * gating for RCS should also be disabled.
-	 */
-	I915_WRITE(GEN7_MISCCPCTL, (I915_READ(GEN7_MISCCPCTL) &
-				    ~GEN7_DOP_CLOCK_GATE_ENABLE));
-	I915_WRITE(GEN6_UCGCTL1, (I915_READ(GEN6_UCGCTL1) |
-				  GEN6_CSUNIT_CLOCK_GATE_DISABLE));
-
-	config_oa_regs(dev_priv, oa_config->mux_regs, oa_config->mux_regs_len);
-
-	/* It apparently takes a fairly long time for a new MUX
+	/*
+	 * It apparently takes a fairly long time for a new MUX
 	 * configuration to be be applied after these register writes.
 	 * This delay duration was derived empirically based on the
 	 * render_basic config but hopefully it covers the maximum
@@ -1612,6 +1594,30 @@ static int hsw_enable_metric_set(struct i915_perf_stream *stream)
 	 * a delay at this location would mitigate any invalid reports.
 	 */
 	usleep_range(15000, 20000);
+}
+
+static int hsw_enable_metric_set(struct i915_perf_stream *stream)
+{
+	struct drm_i915_private *dev_priv = stream->dev_priv;
+	const struct i915_oa_config *oa_config = stream->oa_config;
+
+	/*
+	 * PRM:
+	 *
+	 * OA unit is using “crclk” for its functionality. When trunk
+	 * level clock gating takes place, OA clock would be gated,
+	 * unable to count the events from non-render clock domain.
+	 * Render clock gating must be disabled when OA is enabled to
+	 * count the events from non-render domain. Unit level clock
+	 * gating for RCS should also be disabled.
+	 */
+	I915_WRITE(GEN7_MISCCPCTL, (I915_READ(GEN7_MISCCPCTL) &
+				    ~GEN7_DOP_CLOCK_GATE_ENABLE));
+	I915_WRITE(GEN6_UCGCTL1, (I915_READ(GEN6_UCGCTL1) |
+				  GEN6_CSUNIT_CLOCK_GATE_DISABLE));
+
+	config_oa_regs(dev_priv, oa_config->mux_regs, oa_config->mux_regs_len);
+	delay_after_mux();
 
 	config_oa_regs(dev_priv, oa_config->b_counter_regs,
 		       oa_config->b_counter_regs_len);
@@ -1837,6 +1843,7 @@ static int gen8_enable_metric_set(struct i915_perf_stream *stream)
 		return ret;
 
 	config_oa_regs(dev_priv, oa_config->mux_regs, oa_config->mux_regs_len);
+	delay_after_mux();
 
 	config_oa_regs(dev_priv, oa_config->b_counter_regs,
 		       oa_config->b_counter_regs_len);