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[SRU,Noble,8/8] drm/i915/display: Increase number of fast wake precharge pulses

Message ID 20240416060416.18571-9-hui.wang@canonical.com
State New
Headers show
Series Fix panel flickering issue when i915.psr2 is enabled | expand

Commit Message

Hui Wang April 16, 2024, 6:04 a.m. UTC 
From: Jouni Högander <jouni.hogander@intel.com>

BugLink: https://bugs.launchpad.net/bugs/2046315

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/9739
Signed-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
(cherry picked from commit f77772866385cd0a72311a9e2ac176214d2b0fa8 linux-next)
Signed-off-by: Hui Wang <hui.wang@canonical.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
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Patch

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index 375a94b3d455..375cce5bfc68 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -144,7 +144,13 @@  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;