[PATCH 1/2] drm/i915/hotplug: Reduce SHPD_FLITER_CNT for DISPLAY_VER() == 12

[Suraj Kandpal]

Reduce SHPD_CNT to 250us for display version 12 as it lines up
with DP1.4a(Table3-4) spec.

--v2
-Update commit message and comment [Matt]

Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
---
 drivers/gpu/drm/i915/display/intel_hotplug_irq.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hotplug_irq.c b/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
index 2c4e946d5575..8427386132e6 100644
--- a/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
+++ b/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
@@ -849,7 +849,11 @@ static void icp_hpd_irq_setup(struct drm_i915_private *dev_priv)
 	enabled_irqs = intel_hpd_enabled_irqs(dev_priv, dev_priv->display.hotplug.pch_hpd);
 	hotplug_irqs = intel_hpd_hotplug_irqs(dev_priv, dev_priv->display.hotplug.pch_hpd);
 
-	if (INTEL_PCH_TYPE(dev_priv) <= PCH_TGP)
+	/*
+	 * We reduce the value to 250us to be able to detect SHPD when an external display
+	 * is connected. This is also expected of us as stated in DP1.4a Table 3-4.
+	 */
+	if (INTEL_PCH_TYPE(dev_priv) < PCH_TGP)
 		intel_uncore_write(&dev_priv->uncore, SHPD_FILTER_CNT, SHPD_FILTER_CNT_500_ADJ);
 	else
 		intel_uncore_write(&dev_priv->uncore, SHPD_FILTER_CNT, SHPD_FILTER_CNT_250);
-- 
2.43.2