drm/i915: Workaround broken BIOS DBUF configuration on TGL/RKL

On TGL/RKL the BIOS likes to use some kind of bogus DBUF layout
that doesn't match what the spec recommends. With a single active
pipe that is not going to be a problem, but with multiple pipes
active skl_commit_modeset_enables() goes into an infinite loop
since it can't figure out any order in which it can commit the
pipes without causing DBUF overlaps between the planes.

We'd need some kind of extra DBUF defrag stage in between to
make the transition possible. But that is clearly way too complex
a solution, so in the name of simplicity let's just sanitize the
DBUF state by simply turning off all planes when we detect a
pipe encroaching on its neighbours' DBUF slices. We only have
to disable the primary planes as all other planes should have
already been disabled (if they somehow were enabled) by
earlier sanitization steps.

And for good measure let's also sanitize in case the DBUF
allocations of the pipes already seem to overlap each other.

Cc: <stable@vger.kernel.org> # v5.14+
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4762Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220204141818.1900-3-ville.syrjala@linux.intel.comReviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>

drivers/gpu/drm/i915/display/intel_display.c

@@ -10649,6 +10649,7 @@ intel_modeset_setup_hw_state(struct drm_device *dev,
 		vlv_wm_sanitize(dev_priv);
 	} else if (DISPLAY_VER(dev_priv) >= 9) {
 		skl_wm_get_hw_state(dev_priv);
+		skl_wm_sanitize(dev_priv);
 	} else if (HAS_PCH_SPLIT(dev_priv)) {
 		ilk_wm_get_hw_state(dev_priv);
 	}

drivers/gpu/drm/i915/intel_pm.c

@@ -6710,6 +6710,74 @@ void skl_wm_get_hw_state(struct drm_i915_private *dev_priv)
 	dbuf_state->enabled_slices = dev_priv->dbuf.enabled_slices;
 }
 
+static bool skl_dbuf_is_misconfigured(struct drm_i915_private *i915)
+{
+	const struct intel_dbuf_state *dbuf_state =
+		to_intel_dbuf_state(i915->dbuf.obj.state);
+	struct skl_ddb_entry entries[I915_MAX_PIPES] = {};
+	struct intel_crtc *crtc;
+
+	for_each_intel_crtc(&i915->drm, crtc) {
+		const struct intel_crtc_state *crtc_state =
+			to_intel_crtc_state(crtc->base.state);
+
+		entries[crtc->pipe] = crtc_state->wm.skl.ddb;
+	}
+
+	for_each_intel_crtc(&i915->drm, crtc) {
+		const struct intel_crtc_state *crtc_state =
+			to_intel_crtc_state(crtc->base.state);
+		u8 slices;
+
+		slices = skl_compute_dbuf_slices(crtc, dbuf_state->active_pipes,
+						 dbuf_state->joined_mbus);
+		if (dbuf_state->slices[crtc->pipe] & ~slices)
+			return true;
+
+		if (skl_ddb_allocation_overlaps(&crtc_state->wm.skl.ddb, entries,
+						I915_MAX_PIPES, crtc->pipe))
+			return true;
+	}
+
+	return false;
+}
+
+void skl_wm_sanitize(struct drm_i915_private *i915)
+{
+	struct intel_crtc *crtc;
+
+	/*
+	 * On TGL/RKL (at least) the BIOS likes to assign the planes
+	 * to the wrong DBUF slices. This will cause an infinite loop
+	 * in skl_commit_modeset_enables() as it can't find a way to
+	 * transition between the old bogus DBUF layout to the new
+	 * proper DBUF layout without DBUF allocation overlaps between
+	 * the planes (which cannot be allowed or else the hardware
+	 * may hang). If we detect a bogus DBUF layout just turn off
+	 * all the planes so that skl_commit_modeset_enables() can
+	 * simply ignore them.
+	 */
+	if (!skl_dbuf_is_misconfigured(i915))
+		return;
+
+	drm_dbg_kms(&i915->drm, "BIOS has misprogrammed the DBUF, disabling all planes\n");
+
+	for_each_intel_crtc(&i915->drm, crtc) {
+		struct intel_plane *plane = to_intel_plane(crtc->base.primary);
+		const struct intel_plane_state *plane_state =
+			to_intel_plane_state(plane->base.state);
+		struct intel_crtc_state *crtc_state =
+			to_intel_crtc_state(crtc->base.state);
+
+		if (plane_state->uapi.visible)
+			intel_plane_disable_noatomic(crtc, plane);
+
+		drm_WARN_ON(&i915->drm, crtc_state->active_planes != 0);
+
+		memset(&crtc_state->wm.skl.ddb, 0, sizeof(crtc_state->wm.skl.ddb));
+	}
+}
+
 static void ilk_pipe_wm_get_hw_state(struct intel_crtc *crtc)
 {
 	struct drm_device *dev = crtc->base.dev;

drivers/gpu/drm/i915/intel_pm.h

@@ -46,6 +46,7 @@ void skl_pipe_wm_get_hw_state(struct intel_crtc *crtc,
 			      struct skl_pipe_wm *out);
 void g4x_wm_sanitize(struct drm_i915_private *dev_priv);
 void vlv_wm_sanitize(struct drm_i915_private *dev_priv);
+void skl_wm_sanitize(struct drm_i915_private *dev_priv);
 bool intel_can_enable_sagv(struct drm_i915_private *dev_priv,
 			   const struct intel_bw_state *bw_state);
 void intel_sagv_pre_plane_update(struct intel_atomic_state *state);