[RFC 3/3] drm/i915: add underrun counts to i915_display_info

[Joe Konno <joe.konno@linux.intel.com>]

From: Joe Konno <joe.konno@intel.com>

Add atomic cpu and pch underrun counters to struct intel_crtc, and
increment them each time their respective interrupt handler executes.

Whether dmesg underrun reporting is disabled or not, keep a count of cpu
and pch underrun interrupts. Display these counts in i915_display_info
on a per-pipe. per-transcoder basis to assist debugging and testing.

In debugfs, the i915_display_info output for each pipe changes from
this:
    underrun reporting: cpu=%s pch=%s

to this, where the number of underruns are reported in parentheses:
    underrun reporting: cpu=%s (%d) pch=%s (%d)

Signed-off-by: Joe Konno <joe.konno@intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c        | 6 ++++--
 drivers/gpu/drm/i915/intel_drv.h           | 4 ++++
 drivers/gpu/drm/i915/intel_fifo_underrun.c | 6 ++++++
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 863012a2602e..aa47987bb13b 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -3101,9 +3101,11 @@ static int i915_display_info(struct seq_file *m, void *unused)
 			intel_plane_info(m, crtc);
 		}
 
-		seq_printf(m, "\tunderrun reporting: cpu=%s pch=%s \n",
+		seq_printf(m, "\tunderrun reporting: cpu=%s (%d) pch=%s (%d) \n",
 			   yesno(!crtc->cpu_fifo_underrun_disabled),
-			   yesno(!crtc->pch_fifo_underrun_disabled));
+			   atomic_read(&crtc->cpu_fifo_underrun_count),
+			   yesno(!crtc->pch_fifo_underrun_disabled),
+			   atomic_read(&crtc->pch_fifo_underrun_count));
 	}
 
 	seq_printf(m, "\n");
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index bc970125ec76..efc6eb0a517f 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -589,6 +589,10 @@ struct intel_crtc {
 	/* reset counter value when the last flip was submitted */
 	unsigned int reset_counter;
 
+	/* fifo_underrun counters, used in debugfs only */
+	atomic_t cpu_fifo_underrun_count;
+	atomic_t pch_fifo_underrun_count;
+
 	/* Access to these should be protected by dev_priv->irq_lock. */
 	bool cpu_fifo_underrun_disabled;
 	bool pch_fifo_underrun_disabled;
diff --git a/drivers/gpu/drm/i915/intel_fifo_underrun.c b/drivers/gpu/drm/i915/intel_fifo_underrun.c
index 4a1a2781fc5e..d7b355b831e1 100644
--- a/drivers/gpu/drm/i915/intel_fifo_underrun.c
+++ b/drivers/gpu/drm/i915/intel_fifo_underrun.c
@@ -407,6 +407,9 @@ void intel_cpu_fifo_underrun_irq_handler(struct drm_i915_private *dev_priv,
 
 	report = intel_get_cpu_fifo_underrun_reporting(dev_priv, pipe);
 
+	/* Increment the debugfs underrun counter */
+	atomic_inc(&to_intel_crtc(crtc)->cpu_fifo_underrun_count);
+
 	if (report)
 		DRM_ERROR_RATELIMITED("CPU pipe %c FIFO underrun\n",
 				      pipe_name(pipe));
@@ -427,6 +430,9 @@ void intel_pch_fifo_underrun_irq_handler(struct drm_i915_private *dev_priv,
 	bool report = intel_get_pch_fifo_underrun_reporting(dev_priv,
 							    pch_transcoder);
 
+	/* Increment the debugfs underrun counter */
+	atomic_inc(&to_intel_crtc(crtc)->pch_fifo_underrun_count);
+
 	if (report)
 		DRM_ERROR_RATELIMITED("PCH transcoder %c FIFO underrun\n",
 				      transcoder_name(pch_transcoder));
-- 
2.6.4

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