drm/i915: Fix eDP low vswing for Broadwell

commit 992e7a41f9fcc7bcd10e7d346aee5ed7a2c241cb upstream.

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
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
(cherry picked from commit 00983519214b61c1b9371ec2ed55a4dde773e384)
[Jani: s/dev_priv->vbt.edp.low_vswing/dev_priv->edp_low_vswing/ to backport]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 2effcd42032894dc6c87580b4515860b6013baf2..33b8e0a2b3fd7ad9fcad1f4e25a1708257ac5b23 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -464,9 +464,17 @@ static void intel_prepare_ddi_buffers(struct drm_device *dev, enum port port,
        } else if (IS_BROADWELL(dev)) {
                ddi_translations_fdi = bdw_ddi_translations_fdi;
                ddi_translations_dp = bdw_ddi_translations_dp;
-               ddi_translations_edp = bdw_ddi_translations_edp;
+
+               if (dev_priv->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;