drm/vc4: hvs: Add debugfs node that dumps the current display lists

This allows easy analysis of display lists when debugging.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20220613144800.326124-8-maxime@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/vc4/vc4_hvs.c

@@ -94,6 +94,46 @@ static int vc4_hvs_debugfs_underrun(struct seq_file *m, void *data)
 	return 0;
 }
 
+static int vc4_hvs_debugfs_dlist(struct seq_file *m, void *data)
+{
+	struct drm_info_node *node = m->private;
+	struct drm_device *dev = node->minor->dev;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	struct vc4_hvs *hvs = vc4->hvs;
+	struct drm_printer p = drm_seq_file_printer(m);
+	unsigned int next_entry_start = 0;
+	unsigned int i, j;
+	u32 dlist_word, dispstat;
+
+	for (i = 0; i < SCALER_CHANNELS_COUNT; i++) {
+		dispstat = VC4_GET_FIELD(HVS_READ(SCALER_DISPSTATX(i)),
+					 SCALER_DISPSTATX_MODE);
+		if (dispstat == SCALER_DISPSTATX_MODE_DISABLED ||
+		    dispstat == SCALER_DISPSTATX_MODE_EOF) {
+			drm_printf(&p, "HVS chan %u disabled\n", i);
+			continue;
+		}
+
+		drm_printf(&p, "HVS chan %u:\n", i);
+
+		for (j = HVS_READ(SCALER_DISPLISTX(i)); j < 256; j++) {
+			dlist_word = readl((u32 __iomem *)vc4->hvs->dlist + j);
+			drm_printf(&p, "dlist: %02d: 0x%08x\n", j,
+				   dlist_word);
+			if (!next_entry_start ||
+			    next_entry_start == j) {
+				if (dlist_word & SCALER_CTL0_END)
+					break;
+				next_entry_start = j +
+					VC4_GET_FIELD(dlist_word,
+						      SCALER_CTL0_SIZE);
+			}
+		}
+	}
+
+	return 0;
+}
+
 /* The filter kernel is composed of dwords each containing 3 9-bit
  * signed integers packed next to each other.
  */
@@ -734,6 +774,8 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
 	vc4_debugfs_add_regset32(drm, "hvs_regs", &hvs->regset);
 	vc4_debugfs_add_file(drm, "hvs_underrun", vc4_hvs_debugfs_underrun,
 			     NULL);
+	vc4_debugfs_add_file(drm, "hvs_dlists", vc4_hvs_debugfs_dlist,
+			     NULL);
 
 	return 0;
 }