drm/i915: access the PP_ON_DELAYS/PP_OFF_DELAYS regs only pre GEN5

These registers exist only before GEN5, so currently we may access
undefined registers on VLV/CHV and BXT. Apply the workaround only pre
GEN5.

Since the workaround is relevant only when LVDS is present, for clarity
apply it only if this is the case.

This triggered an unclaimed register access warning on BXT.

v2: (Ville)
- move the workaround to the LVDS init code
- print a debug note about the workaround

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index a16308ad9124..2c2d1f0737c8 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -985,6 +985,18 @@ void intel_lvds_init(struct drm_device *dev)
 		DRM_DEBUG_KMS("LVDS is not present in VBT, but enabled anyway\n");
 	}
 
+	 /* Set the Panel Power On/Off timings if uninitialized. */
+	if (INTEL_INFO(dev_priv)->gen < 5 &&
+	    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);
+
+		DRM_DEBUG_KMS("Panel power timings uninitialized, setting defaults\n");
+	}
+
 	lvds_encoder = kzalloc(sizeof(*lvds_encoder), GFP_KERNEL);
 	if (!lvds_encoder)
 		return;