drm/i915: provide FBC status in debugfs

Tools like powertop want to check the current FBC status and report it
to the user.  So add a debugfs file indicating whether FBC is enabled,
and if not, why.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -477,6 +477,54 @@ static int i915_drpc_info(struct seq_file *m, void *unused)
 	return 0;
 }
 
+static int i915_fbc_status(struct seq_file *m, void *unused)
+{
+	struct drm_info_node *node = (struct drm_info_node *) m->private;
+	struct drm_device *dev = node->minor->dev;
+	struct drm_crtc *crtc;
+	drm_i915_private_t *dev_priv = dev->dev_private;
+	bool fbc_enabled = false;
+
+	if (!dev_priv->display.fbc_enabled) {
+		seq_printf(m, "FBC unsupported on this chipset\n");
+		return 0;
+	}
+
+	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
+		if (!crtc->enabled)
+			continue;
+		if (dev_priv->display.fbc_enabled(crtc))
+			fbc_enabled = true;
+	}
+
+	if (fbc_enabled) {
+		seq_printf(m, "FBC enabled\n");
+	} else {
+		seq_printf(m, "FBC disabled: ");
+		switch (dev_priv->no_fbc_reason) {
+		case FBC_STOLEN_TOO_SMALL:
+			seq_printf(m, "not enough stolen memory");
+			break;
+		case FBC_UNSUPPORTED_MODE:
+			seq_printf(m, "mode not supported");
+			break;
+		case FBC_MODE_TOO_LARGE:
+			seq_printf(m, "mode too large");
+			break;
+		case FBC_BAD_PLANE:
+			seq_printf(m, "FBC unsupported on plane");
+			break;
+		case FBC_NOT_TILED:
+			seq_printf(m, "scanout buffer not tiled");
+			break;
+		default:
+			seq_printf(m, "unknown reason");
+		}
+		seq_printf(m, "\n");
+	}
+	return 0;
+}
+
 static int
 i915_wedged_open(struct inode *inode,
 		 struct file *filp)
@@ -599,6 +647,7 @@ static struct drm_info_list i915_debugfs_list[] = {
 	{"i915_delayfreq_table", i915_delayfreq_table, 0},
 	{"i915_inttoext_table", i915_inttoext_table, 0},
 	{"i915_drpc_info", i915_drpc_info, 0},
+	{"i915_fbc_status", i915_fbc_status, 0},
 };
 #define I915_DEBUGFS_ENTRIES ARRAY_SIZE(i915_debugfs_list)
 

drivers/gpu/drm/i915/i915_dma.c

@@ -1249,6 +1249,7 @@ static void i915_setup_compression(struct drm_device *dev, int size)
 	/* Leave 1M for line length buffer & misc. */
 	compressed_fb = drm_mm_search_free(&dev_priv->vram, size, 4096, 0);
 	if (!compressed_fb) {
+		dev_priv->no_fbc_reason = FBC_STOLEN_TOO_SMALL;
 		i915_warn_stolen(dev);
 		return;
 	}
@@ -1256,6 +1257,7 @@ static void i915_setup_compression(struct drm_device *dev, int size)
 	compressed_fb = drm_mm_get_block(compressed_fb, size, 4096);
 	if (!compressed_fb) {
 		i915_warn_stolen(dev);
+		dev_priv->no_fbc_reason = FBC_STOLEN_TOO_SMALL;
 		return;
 	}
 

drivers/gpu/drm/i915/i915_drv.h

@@ -192,6 +192,14 @@ struct intel_device_info {
 	u8 cursor_needs_physical : 1;
 };
 
+enum no_fbc_reason {
+	FBC_STOLEN_TOO_SMALL, /* not enough space to hold compressed buffers */
+	FBC_UNSUPPORTED_MODE, /* interlace or doublescanned mode */
+	FBC_MODE_TOO_LARGE, /* mode too large for compression */
+	FBC_BAD_PLANE, /* fbc not supported on plane */
+	FBC_NOT_TILED, /* buffer not tiled */
+};
+
 typedef struct drm_i915_private {
 	struct drm_device *dev;
 
@@ -597,6 +605,8 @@ typedef struct drm_i915_private {
 	u8 cur_delay;
 	u8 min_delay;
 	u8 max_delay;
+
+	enum no_fbc_reason no_fbc_reason;
 } drm_i915_private_t;
 
 /** driver private structure attached to each drm_gem_object */

drivers/gpu/drm/i915/intel_display.c

@@ -1188,25 +1188,30 @@ static void intel_update_fbc(struct drm_crtc *crtc,
 	if (intel_fb->obj->size > dev_priv->cfb_size) {
 		DRM_DEBUG_KMS("framebuffer too large, disabling "
 				"compression\n");
+		dev_priv->no_fbc_reason = FBC_STOLEN_TOO_SMALL;
 		goto out_disable;
 	}
 	if ((mode->flags & DRM_MODE_FLAG_INTERLACE) ||
 	    (mode->flags & DRM_MODE_FLAG_DBLSCAN)) {
 		DRM_DEBUG_KMS("mode incompatible with compression, "
 				"disabling\n");
+		dev_priv->no_fbc_reason = FBC_UNSUPPORTED_MODE;
 		goto out_disable;
 	}
 	if ((mode->hdisplay > 2048) ||
 	    (mode->vdisplay > 1536)) {
 		DRM_DEBUG_KMS("mode too large for compression, disabling\n");
+		dev_priv->no_fbc_reason = FBC_MODE_TOO_LARGE;
 		goto out_disable;
 	}
 	if ((IS_I915GM(dev) || IS_I945GM(dev)) && plane != 0) {
 		DRM_DEBUG_KMS("plane not 0, disabling compression\n");
+		dev_priv->no_fbc_reason = FBC_BAD_PLANE;
 		goto out_disable;
 	}
 	if (obj_priv->tiling_mode != I915_TILING_X) {
 		DRM_DEBUG_KMS("framebuffer not tiled, disabling compression\n");
+		dev_priv->no_fbc_reason = FBC_NOT_TILED;
 		goto out_disable;
 	}