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>

4 files changed, 66 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 55340de618ea..96e8b9b2cb32 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/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)
 
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 3afe361ec552..47805a41395e 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/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;
         }
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 7df89ae8172f..953ad64e0553 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/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 */
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index e879885f4754..a483f41e9f22 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/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;
         }