drm/i915: Initialize panel timing registers if VBIOS did not

The time between start of the pixel clock and backlight enable is a basic
panel timing constraint.  If the Panel Power On/Off registers are found
to be 0, assume we are booting without VBIOS initialization and set these
registers to something reasonable.

Change-Id: Ibed6cc10d46bf52fd92e0beb25ae3525b5eef99d
Signed-off-by: Bryan Freed <bfreed@chromium.org>
[ickle: rearranged into a separate function to distinguish its role from
simply parsing the VBIOS tables.]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_dma.c

@@ -1235,7 +1235,7 @@ static int i915_load_modeset_init(struct drm_device *dev,
 	 */
 	dev_priv->allow_batchbuffer = 1;
 
-	ret = intel_init_bios(dev);
+	ret = intel_parse_bios(dev);
 	if (ret)
 		DRM_INFO("failed to find VBIOS tables\n");
 
@@ -2001,6 +2001,9 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	intel_setup_gmbus(dev);
 	intel_opregion_setup(dev);
 
+	/* Make sure the bios did its job and set up vital registers */
+	intel_setup_bios(dev);
+
 	i915_gem_load(dev);
 
 	/* Init HWS */

drivers/gpu/drm/i915/intel_bios.c

@@ -577,7 +577,7 @@ init_vbt_defaults(struct drm_i915_private *dev_priv)
 }
 
 /**
- * intel_init_bios - initialize VBIOS settings & find VBT
+ * intel_parse_bios - find VBT and initialize settings from the BIOS
  * @dev: DRM device
  *
  * Loads the Video BIOS and checks that the VBT exists.  Sets scratch registers
@@ -586,7 +586,7 @@ init_vbt_defaults(struct drm_i915_private *dev_priv)
  * Returns 0 on success, nonzero on failure.
  */
 bool
-intel_init_bios(struct drm_device *dev)
+intel_parse_bios(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct pci_dev *pdev = dev->pdev;
@@ -647,3 +647,20 @@ intel_init_bios(struct drm_device *dev)
 
 	return 0;
 }
+
+/* Ensure that vital registers have been initialised, even if the BIOS
+ * is absent or just failing to do its job.
+ */
+void intel_setup_bios(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	 /* Set the Panel Power On/Off timings if uninitialized. */
+	if ((I915_READ(PP_ON_DELAYS) == 0) && (I915_READ(PP_OFF_DELAYS) == 0)) {
+		/* Set T2 to 40ms and T5 to 200ms */
+		I915_WRITE(PP_ON_DELAYS, 0x019007d0);
+
+		/* Set T3 to 35ms and Tx to 200ms */
+		I915_WRITE(PP_OFF_DELAYS, 0x015e07d0);
+	}
+}

drivers/gpu/drm/i915/intel_bios.h

@@ -467,7 +467,8 @@ struct bdb_edp {
 	struct edp_link_params link_params[16];
 } __attribute__ ((packed));
 
-bool intel_init_bios(struct drm_device *dev);
+void intel_setup_bios(struct drm_device *dev);
+bool intel_parse_bios(struct drm_device *dev);
 
 /*
  * Driver<->VBIOS interaction occurs through scratch bits in