linux-kernel - [PATCH v2] drm/i915/display/lspcon: Increase LSPCON mode settle timeout

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Date:   Wed, 14 Jun 2023 23:54:52 +0000
From:   Pablo Ceballos <pceballos@...gle.com>
To:     David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        "Ville Syrjälä" 
        <ville.syrjala@...ux.intel.com>, Sam Ravnborg <sam@...nborg.org>,
        Pablo Ceballos <pceballos@...gle.com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] drm/i915/display/lspcon: Increase LSPCON mode settle timeout

This is to eliminate all cases of "*ERROR* LSPCON mode hasn't settled",
followed by link training errors. Intel engineers recommended increasing
this timeout and that does resolve the issue.

On some CometLake-based device designs the Parade PS175 takes more than
400ms to settle in PCON mode. 100 reboot trials on one device resulted
in a median settle time of 440ms and a maximum of 444ms. Even after
increasing the timeout to 500ms, 2% of devices still had this error. So
this increases the timeout to 800ms.

Signed-off-by: Pablo Ceballos <pceballos@...gle.com>
---

Changelog since v1:
- Added more details in the commit message

 drivers/gpu/drm/i915/display/intel_lspcon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_lspcon.c b/drivers/gpu/drm/i915/display/intel_lspcon.c
index bb3b5355a0d9..d7299fdc43ad 100644
--- a/drivers/gpu/drm/i915/display/intel_lspcon.c
+++ b/drivers/gpu/drm/i915/display/intel_lspcon.c
@@ -167,7 +167,7 @@ static enum drm_lspcon_mode lspcon_wait_mode(struct intel_lspcon *lspcon,
 	drm_dbg_kms(&i915->drm, "Waiting for LSPCON mode %s to settle\n",
 		    lspcon_mode_name(mode));
 
-	wait_for((current_mode = lspcon_get_current_mode(lspcon)) == mode, 400);
+	wait_for((current_mode = lspcon_get_current_mode(lspcon)) == mode, 800);
 	if (current_mode != mode)
 		drm_err(&i915->drm, "LSPCON mode hasn't settled\n");
 
-- 
2.41.0.162.gfafddb0af9-goog