From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
The DP port/pipe goes wonky if we try to use timings with
hdisplay==4096 on pre-HSW platforms. The link fails to train
and the pipe may not signal vblank interrupts. On HDMI such at
mode works just fine (tested on ELK/SNB/CHV). So let's refuse
such modes on DP on older platforms.
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/display/intel_dp.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 0eb5d66f87a7..c96030761eae 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -493,6 +493,25 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
return 0;
}
+static bool intel_dp_hdisplay_bad(struct drm_i915_private *dev_priv,
+ int hdisplay)
+{
+ /*
+ * Older platforms don't like hdisplay==4096 with DP.
+ *
+ * On ILK/SNB/IVB the pipe seems to be somewhat running (scanline
+ * and frame counter increment), but we don't get vblank interrupts,
+ * and the pipe underruns immediately. The link also doesn't seem
+ * to get trained properly.
+ *
+ * On CHV the vblank interrupts don't seem to disappear but
+ * otherwise the symptoms are similar.
+ *
+ * TODO: confirm the behaviour on HSW+
+ */
+ return hdisplay == 4096 && !HAS_DDI(dev_priv);
+}
+
static enum drm_mode_status
intel_dp_mode_valid(struct drm_connector *connector,
struct drm_display_mode *mode)
@@ -528,6 +547,9 @@ intel_dp_mode_valid(struct drm_connector *connector,
max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
mode_rate = intel_dp_link_required(target_clock, 18);
+ if (intel_dp_hdisplay_bad(dev_priv, mode->hdisplay))
+ return MODE_H_ILLEGAL;
+
/*
* Output bpp is stored in 6.4 format so right shift by 4 to get the
* integer value since we support only integer values of bpp.
@@ -2208,6 +2230,9 @@ intel_dp_compute_config(struct intel_encoder *encoder,
if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
return -EINVAL;
+ if (intel_dp_hdisplay_bad(dev_priv, adjusted_mode->crtc_hdisplay))
+ return -EINVAL;
+
ret = intel_dp_compute_link_config(encoder, pipe_config, conn_state);
if (ret < 0)
return ret;
--
2.21.0
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