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/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 3264cb45..4bad0f7 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -180,6 +180,8 @@
/* Enable the PCH Receiver FDI PLL */
rx_ctl_val = FDI_RX_PLL_ENABLE | FDI_RX_ENHANCE_FRAME_ENABLE |
((intel_crtc->fdi_lanes - 1) << 19);
+ if (dev_priv->fdi_rx_polarity_reversed)
+ rx_ctl_val |= FDI_RX_POLARITY_REVERSED_LPT;
I915_WRITE(_FDI_RXA_CTL, rx_ctl_val);
POSTING_READ(_FDI_RXA_CTL);
udelay(220);