[Intel-gfx] [PATCH v2 03/50] drm/i915/xelpd: Enhanced pipe underrun reporting

[Matt Roper <matthew.d.roper@intel.com>]

XE_LPD brings enhanced underrun recovery:  the hardware can somewhat
mitigate underruns by using an interpolated replacement pixel (soft
underrun) or the previous pixel (hard underrun).  Furthermore, underruns
can now be caused downstream by the port, even if the pipe itself is
operating properly.  The interrupt register and PIPE_STATUS register
give us extra bits to recognize hard/soft underruns and determine
whether the underrun was caused by the port, so we'll use that
information to print some more descriptive errors when underruns occur.

v2:
 - Keep ICL's PIPE_STATUS defined separately from the old GMCH pipe
   status register.  (Ville)
 - Only read/clear the PIPE_STATUS register on platforms with
   display ver >= 11. (Lucas)

Bspec: 50335
Bspec: 50366
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
---
 .../drm/i915/display/intel_fifo_underrun.c    | 65 ++++++++++++++++++-
 drivers/gpu/drm/i915/i915_irq.c               | 14 +++-
 drivers/gpu/drm/i915/i915_reg.h               |  8 +++
 3 files changed, 84 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_fifo_underrun.c b/drivers/gpu/drm/i915/display/intel_fifo_underrun.c
index 9605a1064366..b194453838ac 100644
--- a/drivers/gpu/drm/i915/display/intel_fifo_underrun.c
+++ b/drivers/gpu/drm/i915/display/intel_fifo_underrun.c
@@ -359,6 +359,39 @@ bool intel_set_pch_fifo_underrun_reporting(struct drm_i915_private *dev_priv,
 	return old;
 }
 
+static u32
+underrun_pipestat_mask(struct drm_i915_private *dev_priv)
+{
+	u32 mask = PIPE_FIFO_UNDERRUN_STATUS;
+
+	if (DISPLAY_VER(dev_priv) >= 13)
+		mask |= PIPE_STAT_SOFT_UNDERRUN_XELPD |
+			PIPE_STAT_HARD_UNDERRUN_XELPD |
+			PIPE_STAT_PORT_UNDERRUN_XELPD;
+
+	return mask;
+}
+
+static const char *
+pipe_underrun_reason(u32 pipestat_underruns)
+{
+	if (pipestat_underruns & PIPE_STAT_SOFT_UNDERRUN_XELPD)
+		/*
+		 * Hardware used replacement/interpolated pixels at
+		 * underrun locations.
+		 */
+		return "soft";
+	else if (pipestat_underruns & PIPE_STAT_HARD_UNDERRUN_XELPD)
+		/*
+		 * Hardware used previous pixel value at underrun
+		 * locations.
+		 */
+		return "hard";
+	else
+		/* Old platform or no extra soft/hard bit set */
+		return "FIFO";
+}
+
 /**
  * intel_cpu_fifo_underrun_irq_handler - handle CPU fifo underrun interrupt
  * @dev_priv: i915 device instance
@@ -372,6 +405,7 @@ void intel_cpu_fifo_underrun_irq_handler(struct drm_i915_private *dev_priv,
 					 enum pipe pipe)
 {
 	struct intel_crtc *crtc = intel_get_crtc_for_pipe(dev_priv, pipe);
+	u32 underruns = 0;
 
 	/* We may be called too early in init, thanks BIOS! */
 	if (crtc == NULL)
@@ -382,10 +416,37 @@ void intel_cpu_fifo_underrun_irq_handler(struct drm_i915_private *dev_priv,
 	    crtc->cpu_fifo_underrun_disabled)
 		return;
 
+	/*
+	 * Starting with display version 11, the PIPE_STAT register records
+	 * whether an underrun has happened, and on XELPD+, it will also record
+	 * whether the underrun was soft/hard and whether it was triggered by
+	 * the downstream port logic.  We should clear these bits (which use
+	 * write-1-to-clear logic) too.
+	 *
+	 * Note that although the IIR gives us the same underrun and soft/hard
+	 * information, PIPE_STAT is the only place we can find out whether
+	 * the underrun was caused by the downstream port.
+	 */
+	if (DISPLAY_VER(dev_priv) >= 11) {
+		underruns = intel_uncore_read(&dev_priv->uncore,
+					      ICL_PIPESTATUS(pipe)) &
+			underrun_pipestat_mask(dev_priv);
+		intel_uncore_write(&dev_priv->uncore, ICL_PIPESTATUS(pipe),
+				   underruns);
+	}
+
 	if (intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, false)) {
 		trace_intel_cpu_fifo_underrun(dev_priv, pipe);
-		drm_err(&dev_priv->drm, "CPU pipe %c FIFO underrun\n",
-			pipe_name(pipe));
+
+		if (underruns & PIPE_STAT_PORT_UNDERRUN_XELPD)
+			/* Underrun was caused downstream from the pipes */
+			drm_err(&dev_priv->drm, "Port triggered a %s underrun on pipe %c\n",
+				pipe_underrun_reason(underruns),
+				pipe_name(pipe));
+		else
+			drm_err(&dev_priv->drm, "CPU pipe %c %s underrun\n",
+				pipe_name(pipe),
+				pipe_underrun_reason(underruns));
 	}
 
 	intel_fbc_handle_fifo_underrun_irq(dev_priv);
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 031ca1660ef3..0fe836ffcad3 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2424,6 +2424,18 @@ static u32 gen8_de_pipe_flip_done_mask(struct drm_i915_private *i915)
 		return GEN8_PIPE_PRIMARY_FLIP_DONE;
 }
 
+static u32
+underrun_iir_mask(struct drm_i915_private *dev_priv)
+{
+	u32 mask = GEN8_PIPE_FIFO_UNDERRUN;
+
+	if (DISPLAY_VER(dev_priv) >= 13)
+		mask |= XELPD_PIPE_SOFT_UNDERRUN |
+			XELPD_PIPE_HARD_UNDERRUN;
+
+	return mask;
+}
+
 static irqreturn_t
 gen8_de_irq_handler(struct drm_i915_private *dev_priv, u32 master_ctl)
 {
@@ -2532,7 +2544,7 @@ gen8_de_irq_handler(struct drm_i915_private *dev_priv, u32 master_ctl)
 		if (iir & GEN8_PIPE_CDCLK_CRC_DONE)
 			hsw_pipe_crc_irq_handler(dev_priv, pipe);
 
-		if (iir & GEN8_PIPE_FIFO_UNDERRUN)
+		if (iir & underrun_iir_mask(dev_priv))
 			intel_cpu_fifo_underrun_irq_handler(dev_priv, pipe);
 
 		fault_errors = iir & gen8_de_pipe_fault_mask(dev_priv);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 20d60dd11ea3..6c024a5f1117 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6150,6 +6150,12 @@ enum {
 #define   SKL_BOTTOM_COLOR_CSC_ENABLE	(1 << 30)
 #define SKL_BOTTOM_COLOR(pipe)		_MMIO_PIPE2(pipe, _SKL_BOTTOM_COLOR_A)
 
+#define _ICL_PIPE_A_STATUS			0x70058
+#define ICL_PIPESTATUS(pipe)			_MMIO_PIPE2(pipe, _ICL_PIPE_A_STATUS)
+#define   PIPE_STAT_SOFT_UNDERRUN_XELPD		REG_BIT(28)
+#define   PIPE_STAT_HARD_UNDERRUN_XELPD		REG_BIT(27)
+#define   PIPE_STAT_PORT_UNDERRUN_XELPD		REG_BIT(26)
+
 #define VLV_DPFLIPSTAT				_MMIO(VLV_DISPLAY_BASE + 0x70028)
 #define   PIPEB_LINE_COMPARE_INT_EN		(1 << 29)
 #define   PIPEB_HLINE_INT_EN			(1 << 28)
@@ -7803,6 +7809,8 @@ enum {
 #define  GEN8_PIPE_FIFO_UNDERRUN	(1 << 31)
 #define  GEN8_PIPE_CDCLK_CRC_ERROR	(1 << 29)
 #define  GEN8_PIPE_CDCLK_CRC_DONE	(1 << 28)
+#define  XELPD_PIPE_SOFT_UNDERRUN	(1 << 22)
+#define  XELPD_PIPE_HARD_UNDERRUN	(1 << 21)
 #define  GEN8_PIPE_CURSOR_FAULT		(1 << 10)
 #define  GEN8_PIPE_SPRITE_FAULT		(1 << 9)
 #define  GEN8_PIPE_PRIMARY_FAULT	(1 << 8)
-- 
2.25.4

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