drm/i915: set the LPT FDI RX polarity reversal bit when needed
If we fail to set the bit when needed we get some nice FDI link
training failures (AKA "black screen on VGA output").
While we don't really know how to properly choose whether we need to
set the bit or not (VBT?), just read the initial value set by the BIOS
and store it for later usage.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@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 acf768d..3f75cfa 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3917,6 +3917,7 @@
#define FDI_FS_ERRC_ENABLE (1<<27)
#define FDI_FE_ERRC_ENABLE (1<<26)
#define FDI_DP_PORT_WIDTH_X8 (7<<19)
+#define FDI_RX_POLARITY_REVERSED_LPT (1<<16)
#define FDI_8BPC (0<<16)
#define FDI_10BPC (1<<16)
#define FDI_6BPC (2<<16)