[PATCH v6 4/4] drm/i915/display: Increase number of fast wake precharge pulses

["Jouni Högander" <jouni.hogander@intel.com>]

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.

v2: add comment explaining pulse count is increased

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9739
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index 7e69be100d90..3264026454b2 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -145,7 +145,12 @@ 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 MTL with one PSR2 panel 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;
-- 
2.34.1