[PATCH] drm/i915: add a tracepoint for gpu frequency changes

[Daniel Vetter <daniel.vetter@ffwll.ch>]

We've had and still have too many issues where the gpu turbot doesn't
quite to what it's supposed to do (or what we want it to do).

Adding a tracepoint to track when the desired gpu frequence changes
should help a lot in characterizing and understanding problematic
workloads.

Also, this should be fairly interesting for power tuning (and
especially noticing when the gpu is stuck in high frequencies, as has
happened in the past) and hence for integration into powertop and
similar tools.

Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/i915/i915_trace.h |   15 +++++++++++++++
 drivers/gpu/drm/i915/intel_pm.c   |    2 ++
 2 files changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
index 3c4093d..8134421 100644
--- a/drivers/gpu/drm/i915/i915_trace.h
+++ b/drivers/gpu/drm/i915/i915_trace.h
@@ -430,6 +430,21 @@ TRACE_EVENT(i915_reg_rw,
 		(u32)(__entry->val >> 32))
 );
 
+TRACE_EVENT(intel_gpu_freq_change,
+	    TP_PROTO(u32 freq),
+	    TP_ARGS(freq),
+
+	    TP_STRUCT__entry(
+			     __field(u32, freq)
+			     ),
+
+	    TP_fast_assign(
+			   __entry->freq = freq;
+			   ),
+
+	    TP_printk("new_freq=%u", __entry->freq)
+);
+
 #endif /* _I915_TRACE_H_ */
 
 /* This part must be outside protection */
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index ebe3498..194a72f 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2343,6 +2343,8 @@ void gen6_set_rps(struct drm_device *dev, u8 val)
 	I915_WRITE(GEN6_RP_INTERRUPT_LIMITS, limits);
 
 	dev_priv->rps.cur_delay = val;
+
+	trace_intel_gpu_freq_change(val * 50);
 }
 
 static void gen6_disable_rps(struct drm_device *dev)
-- 
1.7.10.4