[PATCH 4/6] drm/i915: Disable display when fused off

[Damien Lespiau <damien.lespiau@intel.com>]

FUSE_STRAP has a bit to inform us that the display has been fused off.
Use it to setup the definitive number of pipes at run-time.

v2: actually tweak num_pipes, not num_planes
v3: also tests SFUSE_STRAP bit 7

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
---
 drivers/gpu/drm/i915/i915_dma.c | 18 +++++++++++++++++-
 drivers/gpu/drm/i915/i915_reg.h |  1 +
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 0f75d5c7..a95a1c0 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1466,14 +1466,30 @@ static void i915_dump_device_info(struct drm_i915_private *dev_priv)
  *   - it's judged too laborious to fill n static structures with the limit
  *     when a simple if statement does the job,
  *   - run-time checks (eg read fuse/strap registers) are needed.
+ *
+ * This function needs to be called after the MMIO has been setup as we are
+ * reading registers, and before the first usage of the fields it can tweak.
  */
 static void intel_device_info_runtime_init(struct drm_device *dev)
 {
-	struct intel_device_info *info = INTEL_INFO(dev);
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_device_info *info = &dev_priv->info;
 
 	info->num_planes = 1;
 	if (IS_VALLEYVIEW(dev))
 		info->num_planes = 2;
+
+	if ((INTEL_INFO(dev)->gen == 7 || INTEL_INFO(dev)->gen == 8) &&
+	    !IS_VALLEYVIEW(dev)) {
+		u32 fuse_strap = I915_READ(FUSE_STRAP);
+		u32 sfuse_strap = I915_READ(SFUSE_STRAP);
+
+		if (fuse_strap & ILK_INTERNAL_DISPLAY_DISABLE ||
+		    sfuse_strap & SFUSE_STRAP_DISPLAY_DISABLED) {
+			DRM_DEBUG_DRIVER("Display fused off, disabling\n");
+			info->num_pipes = 0;
+		}
+	}
 }
 
 /**
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index c6d9ba5..85e53ed 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5411,6 +5411,7 @@
 
 /* SFUSE_STRAP */
 #define SFUSE_STRAP			0xc2014
+#define  SFUSE_STRAP_DISPLAY_DISABLED	(1<<7)
 #define  SFUSE_STRAP_DDIB_DETECTED	(1<<2)
 #define  SFUSE_STRAP_DDIC_DETECTED	(1<<1)
 #define  SFUSE_STRAP_DDID_DETECTED	(1<<0)
-- 
1.8.3.1