drm/i915: Gather the HDMI level shifter logic into one place

The knowledge about the HDMI/DVI DDI translation table was scattered
around.
  - info->hdmi_level_shift was initialized with 6, the index of the 800
    mV, 0dB translation
  - A check on the VBT value was done to ensure it wasn't overflowing
    the translation table (< 0xC)
  - The actual programming was done in intel_ddi.c

As we need to change that knowledge for Broadwell, let's gather
everything into one place.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index ce30bb3ed566..0d7e55f2a8a2 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1232,6 +1232,12 @@ enum modeset_restore {
 };
 
 struct ddi_vbt_port_info {
+	/*
+	 * This is an index in the HDMI/DVI DDI buffer translation table.
+	 * The special value HDMI_LEVEL_SHIFT_UNKNOWN means the VBT didn't
+	 * populate this field.
+	 */
+#define HDMI_LEVEL_SHIFT_UNKNOWN	0xff
 	uint8_t hdmi_level_shift;
 
 	uint8_t supports_dvi:1;