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drm/i915: WARN if max vswing/pre-emphasis violates the DP spec

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According to the DP spec a DPTX must support vswing/pre-emphasis
up to and including level 2. Level 3 is optional (actually DP 1.4a
seems to make even level 3 mandatory for HBR2/3, while leaving it
optional for RBR/HBR1).

WARN if out encoders' .voltage_max()/.preemph_max() return
an illegal value.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200709145845.18118-1-ville.syrjala@linux.intel.com
This commit is contained in:
Ville Syrjälä 2020-07-09 17:58:45 +03:00 committed by José Roberto de Souza
parent e398d7c126
commit a133c6988f
1 changed files with 9 additions and 0 deletions
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9
drivers/gpu/drm/i915/display/intel_dp_link_training.c
View file

@ -52,6 +52,7 @@ static u8 dp_voltage_max(u8 preemph)
void intel_dp_get_adjust_train(struct intel_dp *intel_dp,
const u8 link_status[DP_LINK_STATUS_SIZE])
{
struct drm_i915_private *i915 = dp_to_i915(intel_dp);
u8 v = 0;
u8 p = 0;
int lane;
@ -64,12 +65,20 @@ void intel_dp_get_adjust_train(struct intel_dp *intel_dp,
}
preemph_max = intel_dp->preemph_max(intel_dp);
drm_WARN_ON_ONCE(&i915->drm,
preemph_max != DP_TRAIN_PRE_EMPH_LEVEL_2 &&
preemph_max != DP_TRAIN_PRE_EMPH_LEVEL_3);
if (p >= preemph_max)
p = preemph_max | DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
v = min(v, dp_voltage_max(p));
voltage_max = intel_dp->voltage_max(intel_dp);
drm_WARN_ON_ONCE(&i915->drm,
voltage_max != DP_TRAIN_VOLTAGE_SWING_LEVEL_2 &&
voltage_max != DP_TRAIN_VOLTAGE_SWING_LEVEL_3);
if (v >= voltage_max)
v = voltage_max | DP_TRAIN_MAX_SWING_REACHED;