drm/i915/bxt: Reversed polarity of PORT_PLL_REF_SEL bit

For BXT, description of polarities of PORT_PLL_REF_SEL
has been reversed for newer Gen9LP steppings according to the
recent update in Bspec. This bit now should be set for
"Non-SSC" mode for all Gen9LP starting from B0 stepping.

v2: Only B0 and newer stepping should be affected by this
change.

Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94866
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458176773-26925-1-git-send-email-dongwon.kim@intel.com

diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c b/drivers/gpu/drm/i915/intel_dpll_mgr.c
index 19efdd3..0bde6a4 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
@@ -1296,7 +1296,15 @@ static void bxt_ddi_pll_enable(struct drm_i915_private *dev_priv,
        enum port port = (enum port)pll->id;    /* 1:1 port->PLL mapping */
 
        temp = I915_READ(BXT_PORT_PLL_ENABLE(port));
-       temp &= ~PORT_PLL_REF_SEL;
+       /*
+        * Definition of each bit polarity has been changed
+        * after A1 stepping
+        */
+       if (IS_BXT_REVID(dev_priv, 0, BXT_REVID_A1))
+               temp &= ~PORT_PLL_REF_SEL;
+       else
+               temp |= PORT_PLL_REF_SEL;
+
        /* Non-SSC reference */
        I915_WRITE(BXT_PORT_PLL_ENABLE(port), temp);