[PATCH 2/2] drm/i915/hotplug: Add comment for XE_LPD+ SHPD_FILTER_CNT value

[Suraj Kandpal]

Add the reason for having SHPD_FILTER_CNT value for XE_LPD+ and
above as 250us instead of 500us.

--v2
-Update commit message [Matt]

Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
Reviewed-by: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/i915/display/intel_hotplug_irq.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_hotplug_irq.c b/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
index 8427386132e6..f28f35121e5a 100644
--- a/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
+++ b/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
@@ -1064,6 +1064,10 @@ static void mtp_hpd_irq_setup(struct drm_i915_private *i915)
 	enabled_irqs = intel_hpd_enabled_irqs(i915, i915->display.hotplug.pch_hpd);
 	hotplug_irqs = intel_hpd_hotplug_irqs(i915, i915->display.hotplug.pch_hpd);
 
+	/*
+	 * Use 250us here to align with the DP1.4a(Table 3-4) spec as to what the
+	 * SHPD_FILTER_CNT value should be.
+	 */
 	intel_de_write(i915, SHPD_FILTER_CNT, SHPD_FILTER_CNT_250);
 
 	mtp_hpd_invert(i915);
-- 
2.43.2