drm/v3d: Dump V3D error debug registers in debugfs, and one at reset.

Looking at a hang recently, I noticed these registers that might tell
me if something obvious was wrong.  They didn't help in this case, but
keep it around for the future.
Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190419001014.23579-3-eric@anholt.netReviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

drivers/gpu/drm/v3d/v3d_debugfs.c

@@ -58,6 +58,11 @@ static const struct v3d_reg_def v3d_core_reg_defs[] = {
 	REGDEF(V3D_GMP_STATUS),
 	REGDEF(V3D_GMP_CFG),
 	REGDEF(V3D_GMP_VIO_ADDR),
+
+	REGDEF(V3D_ERR_FDBGO),
+	REGDEF(V3D_ERR_FDBGB),
+	REGDEF(V3D_ERR_FDBGS),
+	REGDEF(V3D_ERR_STAT),
 };
 
 static const struct v3d_reg_def v3d_csd_reg_defs[] = {

drivers/gpu/drm/v3d/v3d_gem.c

@@ -109,7 +109,9 @@ v3d_reset(struct v3d_dev *v3d)
 {
 	struct drm_device *dev = &v3d->drm;
 
-	DRM_ERROR("Resetting GPU.\n");
+	DRM_DEV_ERROR(dev->dev, "Resetting GPU for hang.\n");
+	DRM_DEV_ERROR(dev->dev, "V3D_ERR_STAT: 0x%08x\n",
+		      V3D_CORE_READ(0, V3D_ERR_STAT));
 	trace_v3d_reset_begin(dev);
 
 	/* XXX: only needed for safe powerdown, not reset. */

drivers/gpu/drm/v3d/v3d_regs.h

@@ -455,4 +455,42 @@
 # define V3D_CSD_CURRENT_ID0_WG_Y_MASK                 V3D_MASK(15, 0)
 # define V3D_CSD_CURRENT_ID0_WG_Y_SHIFT                0
 
+#define V3D_ERR_FDBGO                                  0x00f04
+#define V3D_ERR_FDBGB                                  0x00f08
+#define V3D_ERR_FDBGR                                  0x00f0c
+
+#define V3D_ERR_FDBGS                                  0x00f10
+# define V3D_ERR_FDBGS_INTERPZ_IP_STALL                BIT(17)
+# define V3D_ERR_FDBGS_DEPTHO_FIFO_IP_STALL            BIT(16)
+# define V3D_ERR_FDBGS_XYNRM_IP_STALL                  BIT(14)
+# define V3D_ERR_FDBGS_EZREQ_FIFO_OP_VALID             BIT(13)
+# define V3D_ERR_FDBGS_QXYF_FIFO_OP_VALID              BIT(12)
+# define V3D_ERR_FDBGS_QXYF_FIFO_OP_LAST               BIT(11)
+# define V3D_ERR_FDBGS_EZTEST_ANYQVALID                BIT(7)
+# define V3D_ERR_FDBGS_EZTEST_PASS                     BIT(6)
+# define V3D_ERR_FDBGS_EZTEST_QREADY                   BIT(5)
+# define V3D_ERR_FDBGS_EZTEST_VLF_OKNOVALID            BIT(4)
+# define V3D_ERR_FDBGS_EZTEST_QSTALL                   BIT(3)
+# define V3D_ERR_FDBGS_EZTEST_IP_VLFSTALL              BIT(2)
+# define V3D_ERR_FDBGS_EZTEST_IP_PRSTALL               BIT(1)
+# define V3D_ERR_FDBGS_EZTEST_IP_QSTALL                BIT(0)
+
+#define V3D_ERR_STAT                                   0x00f20
+# define V3D_ERR_L2CARE                                BIT(15)
+# define V3D_ERR_VCMBE                                 BIT(14)
+# define V3D_ERR_VCMRE                                 BIT(13)
+# define V3D_ERR_VCDI                                  BIT(12)
+# define V3D_ERR_VCDE                                  BIT(11)
+# define V3D_ERR_VDWE                                  BIT(10)
+# define V3D_ERR_VPMEAS                                BIT(9)
+# define V3D_ERR_VPMEFNA                               BIT(8)
+# define V3D_ERR_VPMEWNA                               BIT(7)
+# define V3D_ERR_VPMERNA                               BIT(6)
+# define V3D_ERR_VPMERR                                BIT(5)
+# define V3D_ERR_VPMEWR                                BIT(4)
+# define V3D_ERR_VPAERRGL                              BIT(3)
+# define V3D_ERR_VPAEBRGL                              BIT(2)
+# define V3D_ERR_VPAERGS                               BIT(1)
+# define V3D_ERR_VPAEABB                               BIT(0)
+
 #endif /* V3D_REGS_H */