linux-kernel - [PATCH 4.2.y-ckt 21/59] drm/i915: Fix eDP low vswing for Broadwell

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Message-Id: <1462823777-8384-22-git-send-email-kamal@canonical.com>
Date:	Mon,  9 May 2016 12:55:39 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Mika Kahola <mika.kahola@...el.com>,
	Ville Syrjälä 
	<ville.syrjala@...ux.intel.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 21/59] drm/i915: Fix eDP low vswing for Broadwell

4.2.8-ckt10 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Mika Kahola <mika.kahola@...el.com>

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@...el.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@...ux.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@...el.com>

Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/gpu/drm/i915/intel_ddi.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index cca3816..8c443c9 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -296,9 +296,17 @@ 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;
-- 
2.7.4