drm/i915: Increase LSPCON timeout

commit 299c2a9 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: 357c0ae ("drm/i915/lspcon: Wait for expected LSPCON mode to settle")
Cc: Shashank Sharma <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: <[email protected]> # v4.11+
Reviewed-by: Rodrigo Vivi <[email protected]>
Reviewed-by: Shashank Sharma <[email protected]>
Signed-off-by: Fredrik Schön <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit 59f1c8a)
Signed-off-by: Rodrigo Vivi <[email protected]>
Reviewed-by: Shashank Sharma <[email protected]>
Signed-off-by: Fredrik Schön <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Fredrik Schön

drivers/gpu/drm/i915/intel_lspcon.c

@@ -75,7 +75,7 @@ static enum drm_lspcon_mode lspcon_wait_mode(struct intel_lspcon *lspcon,
 		      lspcon_mode_name(mode));
 
 	wait_for((current_mode = lspcon_get_current_mode(lspcon)) == mode ||
-		 current_mode == DRM_LSPCON_MODE_INVALID, 100);
+                current_mode == DRM_LSPCON_MODE_INVALID, 400);
 	if (current_mode != mode)
 		DRM_DEBUG_KMS("LSPCON mode hasn't settled\n");