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[14/38,SRU,G/H] drm/i915: Fix DP_TRAIN_MAX_{PRE_EMPHASIS, SWING}_REACHED handling

Message ID 20201124104313.421860-15-vicamo.yang@canonical.com
State New
Headers show
Series Add DRM support for LTTPR non-transparent link training mode | expand

Commit Message

You-Sheng Yang Nov. 24, 2020, 10:42 a.m. UTC
From: Ville Syrjälä <ville.syrjala@linux.intel.com>

BugLink: https://bugs.launchpad.net/bugs/1903969

The DP spec says:
"The transmitter shall support at least three levels of voltage
 swing (Levels 0, 1, and 2).

 If only three levels of voltage swing are supported (VOLTAGE
 SWING SET field (bits 1:0) are programmed to 10 (Level 2)),
 this bit shall be set to 1, and cleared in all other cases.

 If all four levels of voltage swing are supported (VOLTAGE
 SWING SET field (bits 1:0) are programmed to 11 (Level 3)),
 this bit shall be set to 1,and cleared in all other cases."

Let's follow that exactly instead of the current apporach
where we can set those also for vswing/preemph levels 0 or 1
(or 2 when the platform max is 3).

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200512174145.3186-7-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>
(cherry picked from commit 3625a1f5bf6ba47fbd903be1d63dade9a48e8e72)
Signed-off-by: You-Sheng Yang <vicamo.yang@canonical.com>
 drivers/gpu/drm/i915/display/intel_dp_link_training.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
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diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index b9e4ee2dbddc..2493142a70e9 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -67,8 +67,9 @@  void intel_dp_get_adjust_train(struct intel_dp *intel_dp,
 	if (p >= preemph_max)
-	voltage_max = min(intel_dp->voltage_max(intel_dp),
-			  dp_voltage_max(p));
+	v = min(v, dp_voltage_max(p));
+	voltage_max = intel_dp->voltage_max(intel_dp);
 	if (v >= voltage_max)
 		v = voltage_max | DP_TRAIN_MAX_SWING_REACHED;