drm/i915: Use 18 fast wake AUX sync len

[ Upstream commit 2d6f2f7 ]

HW default for wake sync pulses is 18. 10 precharge and 8 preamble. There
is no reason to change this especially as it is causing problems with
certain eDP panels.

v3: Change "Fixes:" commit
v2: Remove "fast wake" repeat from subject

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Fixes: e1c71f8 ("drm/i915: Fix fast wake AUX sync len")
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8475
Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230530101649.2549949-1-jouni.hogander@intel.com
(cherry picked from commit b29a20f)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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

@@ -127,7 +127,7 @@ static int intel_dp_aux_sync_len(void)
 
 static int intel_dp_aux_fw_sync_len(void)
 {
-	int precharge = 16; /* 10-16 */
+	int precharge = 10; /* 10-16 */
 	int preamble = 8;
 
 	return precharge + preamble;