drm/i915: clear the FPGA_DBG_RM_NOCLAIM bit at driver init

Otherwise, if the BIOS did anything wrong, our first I915_{WRITE,READ}
will give us "unclaimed register"  messages.

V2: Even earlier.
V3: Move it to intel_early_sanitize_regs.

Bugzilla: http://bugs.freedesktop.org/show_bug.cgi?id=58897
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 4fa6beb14c77..e16099b6f942 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1453,6 +1453,22 @@ static void i915_dump_device_info(struct drm_i915_private *dev_priv)
 }
 
 /**
+ * intel_early_sanitize_regs - clean up BIOS state
+ * @dev: DRM device
+ *
+ * This function must be called before we do any I915_READ or I915_WRITE. Its
+ * purpose is to clean up any state left by the BIOS that may affect us when
+ * reading and/or writing registers.
+ */
+static void intel_early_sanitize_regs(struct drm_device *dev)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+
+        if (IS_HASWELL(dev))
+                I915_WRITE_NOTRACE(FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
+}
+
+/**
  * i915_driver_load - setup chip and create an initial config
  * @dev: DRM device
  * @flags: startup flags
@@ -1542,6 +1558,8 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
                 goto put_gmch;
         }
 
+        intel_early_sanitize_regs(dev);
+
         aperture_size = dev_priv->gtt.mappable_end;
 
         dev_priv->gtt.mappable =