drm/i915/display: Increase number of fast wake precharge pulses

Increasing number of fast wake sync pulses seem to fix problems with
certain PSR panels. This should be ok for other panels as well as the eDP
specification allows 10...16 precharge pulses and we are still within that
range.

v3: mention laptop model and panel manufacturer and model in comment
v2: add comment explaining pulse count is increased

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9739Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240313133221.868391-5-jouni.hogander@intel.com

drivers/gpu/drm/i915/display/intel_dp_aux.c

@@ -145,7 +145,13 @@ static int intel_dp_aux_sync_len(void)
 
 int intel_dp_aux_fw_sync_len(void)
 {
-	int precharge = 10; /* 10-16 */
+	/*
+	 * We faced some glitches on Dell Precision 5490 MTL laptop with panel:
+	 * "Manufacturer: AUO, Model: 63898" when using HW default 18. Using 20
+	 * is fixing these problems with the panel. It is still within range
+	 * mentioned in eDP specification.
+	 */
+	int precharge = 12; /* 10-16 */
 	int preamble = 8;
 
 	return precharge + preamble;