drm/i915/bxt: DSI enable for BXT

This patch contains following changes:
1. MIPI device ready changes to support dsi_pre_enable. Changes
   are specific to BXT device ready sequence. Added check for
   ULPS mode(No effects on VLV).
2. Changes in dsi_enable to pick BXT port control register.
3. Changes in dsi_pre_enable to restrict DPIO programming for VLV

v2: Fixed Jani's review comments. Removed the changes in VLV/CHV
    code. Fixed the macros to get proper port offsets.

v3: Rebased on latest drm-nightly branch. Fixed Jani's review comments.

Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index a1c313f..87de3a0 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -7588,6 +7588,13 @@
 #define _MIPIA_PORT_CTRL			(VLV_DISPLAY_BASE + 0x61190)
 #define _MIPIC_PORT_CTRL			(VLV_DISPLAY_BASE + 0x61700)
 #define MIPI_PORT_CTRL(port)	_MIPI_PORT(port, _MIPIA_PORT_CTRL, _MIPIC_PORT_CTRL)
+
+ /* BXT port control */
+#define _BXT_MIPIA_PORT_CTRL				0x6B0C0
+#define _BXT_MIPIC_PORT_CTRL				0x6B8C0
+#define BXT_MIPI_PORT_CTRL(tc)	_MIPI_PORT(tc, _BXT_MIPIA_PORT_CTRL, \
+						_BXT_MIPIC_PORT_CTRL)
+
 #define  DPI_ENABLE					(1 << 31) /* A + C */
 #define  MIPIA_MIPI4DPHY_DELAY_COUNT_SHIFT		27
 #define  MIPIA_MIPI4DPHY_DELAY_COUNT_MASK		(0xf << 27)