From a8899b8728013c7b2456f0bfa20e5fea85ee0fd1 Mon Sep 17 00:00:00 2001
From: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Date: Mon, 21 Nov 2022 15:56:54 +0100
Subject: [PATCH] drm/i915: Fix negative value passed as remaining time
Git-commit: a8899b8728013c7b2456f0bfa20e5fea85ee0fd1
Patch-mainline: v6.1-rc8
Alt-commit: f235dbd5b768e238d365fd05d92de5a32abc1c1f
References: git-fixes
Alt-commit: 6a5347293992e0412bc748dae11228a7081393fa

Commit b97060a99b01 ("drm/i915/guc: Update intel_gt_wait_for_idle to work
with GuC") extended the API of intel_gt_retire_requests_timeout() with an
extra argument 'remaining_timeout', intended for passing back unconsumed
portion of requested timeout when 0 (success) is returned.  However, when
request retirement happens to succeed despite an error returned by a call
to dma_fence_wait_timeout(), that error code (a negative value) is passed
back instead of remaining time.  If we then pass that negative value
forward as requested timeout to intel_uc_wait_for_idle(), an explicit BUG
will be triggered.

If request retirement succeeds but an error code is passed back via
remaininig_timeout, we may have no clue on how much of the initial timeout
might have been left for spending it on waiting for GuC to become idle.
OTOH, since all pending requests have been successfully retired, that
error code has been already ignored by intel_gt_retire_requests_timeout(),
then we shouldn't fail.

Assume no more time has been left on error and pass 0 timeout value to
intel_uc_wait_for_idle() to give it a chance to return success if GuC is
already idle.

V3: Don't fail on any error passed back via remaining_timeout.

V2: Fix the issue on the caller side, not the provider.

Fixes: b97060a99b01 ("drm/i915/guc: Update intel_gt_wait_for_idle to work with GuC")
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: stable@vger.kernel.org # v5.15+
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221121145655.75141-2-janusz.krzysztofik@linux.intel.com
(cherry picked from commit f235dbd5b768e238d365fd05d92de5a32abc1c1f)

Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/gt/intel_gt.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index d0b03a928b9a..9f0388b3dcf2 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -625,8 +625,13 @@ int intel_gt_wait_for_idle(struct intel_gt *gt, long timeout)
 			return -EINTR;
 	}
 
-	return timeout ? timeout : intel_uc_wait_for_idle(&gt->uc,
-							  remaining_timeout);
+	if (timeout)
+		return timeout;
+
+	if (remaining_timeout < 0)
+		remaining_timeout = 0;
+
+	return intel_uc_wait_for_idle(&gt->uc, remaining_timeout);
 }
 
 int intel_gt_init(struct intel_gt *gt)
-- 
2.35.3