drm/i915: Never return 0 if not all requests retired

commit 12b8b046e4c9de40fa59b6f067d6826f4e688f68 upstream.

Users of intel_gt_retire_requests_timeout() expect 0 return value on
success.  However, we have no protection from passing back 0 potentially
returned by a call to dma_fence_wait_timeout() when it succedes right
after its timeout has expired.

Replace 0 with -ETIME before potentially using the timeout value as return
code, so -ETIME is returned if there are still some requests not retired
after timeout, 0 otherwise.

v3: Use conditional expression, more compact but also better reflecting
    intention standing behind the change.

v2: Move the added lines down so flush_submission() is not affected.

Fixes: f33a8a5160 ("drm/i915: Merge wait_for_timelines with retire_request")
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: stable@vger.kernel.org # v5.5+
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221121145655.75141-3-janusz.krzysztofik@linux.intel.com
(cherry picked from commit f301a29f143760ce8d3d6b6a8436d45d3448cde6)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/i915/gt/intel_gt_requests.c

@@ -200,7 +200,7 @@ out_active:	spin_lock(&timelines->lock);
 	if (flush_submission(gt, timeout)) /* Wait, there's more! */
 		active_count++;
 
-	return active_count ? timeout : 0;
+	return active_count ? timeout ?: -ETIME : 0;
 }
 
 int intel_gt_wait_for_idle(struct intel_gt *gt, long timeout)