drm/i915: Fix eDP low vswing for Broadwell

It was noticed on bug #94087 that module parameter
i915.edp_vswing=2 that should override the VBT setting
to use default voltage swing (400 mV) was not applied
for Broadwell.

This patch provides a fix for this by checking if default
i.e. higher voltage swing is requested to be used and
applies the DDI translations table for DP instead of eDP
(low vswing) table.

v2: Combine two if statements into one (Jani)
v3: Change dev_priv->edp_low_vswing to use dev_priv->vbt.edp.low_vswing

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94087
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461155942-7749-1-git-send-email-mika.kahola@intel.com
Cc: stable@vger.kernel.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index c2348fbe9b705366dcafce66349cdf483637c6dc..a887b31cb684268740dde32efbc19f94fb6b43fb 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -443,9 +443,17 @@ void intel_prepare_ddi_buffer(struct intel_encoder *encoder)
        } else if (IS_BROADWELL(dev_priv)) {
                ddi_translations_fdi = bdw_ddi_translations_fdi;
                ddi_translations_dp = bdw_ddi_translations_dp;
-               ddi_translations_edp = bdw_ddi_translations_edp;
+
+               if (dev_priv->vbt.edp.low_vswing) {
+                       ddi_translations_edp = bdw_ddi_translations_edp;
+                       n_edp_entries = ARRAY_SIZE(bdw_ddi_translations_edp);
+               } else {
+                       ddi_translations_edp = bdw_ddi_translations_dp;
+                       n_edp_entries = ARRAY_SIZE(bdw_ddi_translations_dp);
+               }
+
                ddi_translations_hdmi = bdw_ddi_translations_hdmi;
-               n_edp_entries = ARRAY_SIZE(bdw_ddi_translations_edp);
+
                n_dp_entries = ARRAY_SIZE(bdw_ddi_translations_dp);
                n_hdmi_entries = ARRAY_SIZE(bdw_ddi_translations_hdmi);
                hdmi_default_entry = 7;