linux-kernel - [PATCH 4.18 154/197] drm/i915: Increase LSPCON timeout

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Date:   Thu, 13 Sep 2018 15:31:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Shashank Sharma <shashank.sharma@...el.com>,
        Imre Deak <imre.deak@...el.com>,
        Jani Nikula <jani.nikula@...el.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Fredrik Schön <fredrik.schon@...il.com>
Subject: [PATCH 4.18 154/197] drm/i915: Increase LSPCON timeout

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Fredrik Schön <fredrikschon@...il.com>

commit 299c2a904b1e8d5096d4813df6371357d97a6cd1 upstream.

100 ms is not enough time for the LSPCON adapter on Intel NUC devices to
settle. This causes dropped display modes at boot or screen reconfiguration.
Empirical testing can reproduce the error up to a timeout of 190 ms. Basic
boot and stress testing at 200 ms has not (yet) failed.

Increase timeout to 400 ms to get some margin of error.

Changes from v1:
The initial suggestion of 1000 ms was lowered due to concerns about delaying
valid timeout cases.
Update patch metadata.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107503
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1570392
Fixes: 357c0ae9198a ("drm/i915/lspcon: Wait for expected LSPCON mode to settle")
Cc: Shashank Sharma <shashank.sharma@...el.com>
Cc: Imre Deak <imre.deak@...el.com>
Cc: Jani Nikula <jani.nikula@...el.com>
Cc: <stable@...r.kernel.org> # v4.11+
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
Reviewed-by: Shashank Sharma <shashank.sharma@...el.com>
Signed-off-by: Fredrik Schön <fredrik.schon@...il.com>
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180817200728.8154-1-fredrik.schon@gmail.com
(cherry picked from commit 59f1c8ab30d6f9042562949f42cbd3f3cf69de94)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/gpu/drm/i915/intel_lspcon.c
+++ b/drivers/gpu/drm/i915/intel_lspcon.c
@@ -74,7 +74,7 @@ static enum drm_lspcon_mode lspcon_wait_
 	DRM_DEBUG_KMS("Waiting for LSPCON mode %s to settle\n",
 		      lspcon_mode_name(mode));
 
-	wait_for((current_mode = lspcon_get_current_mode(lspcon)) == mode, 100);
+	wait_for((current_mode = lspcon_get_current_mode(lspcon)) == mode, 400);
 	if (current_mode != mode)
 		DRM_ERROR("LSPCON mode hasn't settled\n");