drm/i915/execlists: Always clear pending&inflight requests on reset

If we skip the reset as we found the engine inactive at the time of the
reset, we still need to clear the residual inflight & pending request
bookkeeping to reflect the current state of HW.

Otherwise, we may end up stuck in a loop like:

<7> [416.490346] hangcheck rcs0
<7> [416.490371] hangcheck 	Awake? 1
<7> [416.490376] hangcheck 	Hangcheck: 8003 ms ago
<7> [416.490380] hangcheck 	Reset count: 0 (global 0)
<7> [416.490383] hangcheck 	Requests:
<7> [416.491210] hangcheck 	RING_START: 0x0017b000
<7> [416.491983] hangcheck 	RING_HEAD:  0x00000048
<7> [416.491992] hangcheck 	RING_TAIL:  0x00000048
<7> [416.492006] hangcheck 	RING_CTL:   0x00000000
<7> [416.492037] hangcheck 	RING_MODE:  0x00000200 [idle]
<7> [416.492044] hangcheck 	RING_IMR: 00000000
<7> [416.492809] hangcheck 	ACTHD:  0x00000000_9ca00048
<7> [416.492824] hangcheck 	BBADDR: 0x00000000_00001004
<7> [416.492838] hangcheck 	DMA_FADDR: 0x00000000_00000000
<7> [416.492845] hangcheck 	IPEIR: 0x00000000
<7> [416.492852] hangcheck 	IPEHR: 0x00000000
<7> [416.492863] hangcheck 	Execlist status: 0x00018001 00000000, entries 12
<7> [416.492869] hangcheck 	Execlist CSB read 1, write 1, tasklet queued? no (enabled)
<7> [416.492938] hangcheck 		Pending[0] ring:{start:0017b000, hwsp:fedf9000, seqno:00016fd6}, rq:  20ffa:16fd6!+  prio=-4094 @ 8307ms: signaled
<7> [416.492972] hangcheck 		Queue priority hint: -4093
<7> [416.492979] hangcheck 		Q  20ffa:16fd8-  prio=-4093 @ 8307ms: [i915]
<7> [416.492985] hangcheck 		Q  20ffa:16fda  prio=-4094 @ 8307ms: [i915]
<7> [416.492990] hangcheck 		Q  20ffa:16fdc  prio=-4094 @ 8307ms: [i915]
<7> [416.492996] hangcheck 		Q  20ffa:16fde  prio=-4094 @ 8307ms: [i915]
<7> [416.493001] hangcheck 		Q  20ffa:16fe0  prio=-4094 @ 8307ms: [i915]
<7> [416.493007] hangcheck 		Q  20ffa:16fe2  prio=-4094 @ 8307ms: [i915]
<7> [416.493013] hangcheck 		Q  20ffa:16fe4  prio=-4094 @ 8307ms: [i915]
<7> [416.493021] hangcheck 		...skipping 21 queued requests...
<7> [416.493027] hangcheck 		Q  20ffa:17010  prio=-4094 @ 8307ms: [i915]
<7> [416.493081] hangcheck HWSP:
<7> [416.493089] hangcheck [0000] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
<7> [416.493094] hangcheck *
<7> [416.493100] hangcheck [0040] 10008002 00000000 10000018 00000000 10000018 00000000 10000001 00000000
<7> [416.493106] hangcheck [0060] 10000018 00000000 10000001 00000000 10000018 00000000 10000001 00000000
<7> [416.493111] hangcheck *
<7> [416.493117] hangcheck [00a0] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000001
<7> [416.493123] hangcheck [00c0] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
<7> [416.493127] hangcheck *
<7> [416.493132] hangcheck Idle? no
<6> [416.512124] i915 0000:00:02.0: GPU HANG: ecode 11:0:0x00000000, hang on rcs0
<6> [416.512205] [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
<6> [416.512207] [drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI -> DRM/Intel
<6> [416.512208] [drm] drm/i915 developers can then reassign to the right component if it's not a kernel issue.
<6> [416.512210] [drm] The gpu crash dump is required to analyze gpu hangs, so please always attach it.
<6> [416.512212] [drm] GPU crash dump saved to /sys/class/drm/card0/error
<5> [416.513602] i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
<7> [424.489258] hangcheck rcs0
<7> [424.489263] hangcheck 	Awake? 1
<7> [424.489267] hangcheck 	Hangcheck: 5954 ms ago
<7> [424.489271] hangcheck 	Reset count: 1 (global 0)
<7> [424.489274] hangcheck 	Requests:
<7> [424.490128] hangcheck 	RING_START: 0x00000000
<7> [424.490870] hangcheck 	RING_HEAD:  0x00000000
<7> [424.490877] hangcheck 	RING_TAIL:  0x00000000
<7> [424.490887] hangcheck 	RING_CTL:   0x00000000
<7> [424.490897] hangcheck 	RING_MODE:  0x00000200 [idle]
<7> [424.490904] hangcheck 	RING_IMR: 00000000
<7> [424.490917] hangcheck 	ACTHD:  0x00000000_00000000
<7> [424.490930] hangcheck 	BBADDR: 0x00000000_00000000
<7> [424.490943] hangcheck 	DMA_FADDR: 0x00000000_00000000
<7> [424.490950] hangcheck 	IPEIR: 0x00000000
<7> [424.490956] hangcheck 	IPEHR: 0x00000000
<7> [424.490968] hangcheck 	Execlist status: 0x00000001 00000000, entries 12
<7> [424.490972] hangcheck 	Execlist CSB read 11, write 11, tasklet queued? no (enabled)
<7> [424.490983] hangcheck 		Pending[0] ring:{start:0017b000, hwsp:fedf9000, seqno:00016fd6}, rq:  20ffa:16fd6!+  prio=-4094 @ 16305ms: signaled
<7> [424.490989] hangcheck 		Queue priority hint: -4093
<7> [424.490996] hangcheck 		Q  20ffa:16fd8-  prio=-4093 @ 16305ms: [i915]
<7> [424.491001] hangcheck 		Q  20ffa:16fda  prio=-4094 @ 16305ms: [i915]
<7> [424.491006] hangcheck 		Q  20ffa:16fdc  prio=-4094 @ 16305ms: [i915]
<7> [424.491011] hangcheck 		Q  20ffa:16fde  prio=-4094 @ 16305ms: [i915]
<7> [424.491016] hangcheck 		Q  20ffa:16fe0  prio=-4094 @ 16305ms: [i915]
<7> [424.491022] hangcheck 		Q  20ffa:16fe2  prio=-4094 @ 16305ms: [i915]
<7> [424.491048] hangcheck 		Q  20ffa:16fe4  prio=-4094 @ 16305ms: [i915]
<7> [424.491057] hangcheck 		...skipping 21 queued requests...
<7> [424.491063] hangcheck 		Q  20ffa:17010  prio=-4094 @ 16305ms: [i915]
<7> [424.491095] hangcheck HWSP:
<7> [424.491102] hangcheck [0000] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
<7> [424.491106] hangcheck *
<7> [424.491113] hangcheck [0040] 10008002 00000000 10000018 00000000 10000018 00000000 10000001 00000000
<7> [424.491118] hangcheck [0060] 10000018 00000000 10000001 00000000 10000018 00000000 10000001 00000000
<7> [424.491122] hangcheck *
<7> [424.491127] hangcheck [00a0] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 0000000b
<7> [424.491133] hangcheck [00c0] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
<7> [424.491136] hangcheck *
<7> [424.491141] hangcheck Idle? no
<5> [424.491834] i915 0000:00:02.0: Resetting rcs0 for hang on rcs0

Where not having cleared the pending array on reset, it persists
indefinitely.

Fixes: fff8102a ("drm/i915/execlists: Process interrupted context on reset")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190730133035.1977-2-chris@chris-wilson.co.uk

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

@@ -2280,18 +2280,6 @@ static void __execlists_reset(struct intel_engine_cs *engine, bool stalled)
 	GEM_BUG_ON(i915_active_is_idle(&ce->active));
 	GEM_BUG_ON(!i915_vma_is_pinned(ce->state));
 	rq = active_request(rq);
-
-	/*
-	 * Catch up with any missed context-switch interrupts.
-	 *
-	 * Ideally we would just read the remaining CSB entries now that we
-	 * know the gpu is idle. However, the CSB registers are sometimes^W
-	 * often trashed across a GPU reset! Instead we have to rely on
-	 * guessing the missed context-switch events by looking at what
-	 * requests were completed.
-	 */
-	execlists_cancel_port_requests(execlists);
-
 	if (!rq) {
 		ce->ring->head = ce->ring->tail;
 		goto out_replay;
@@ -2353,6 +2341,7 @@ static void __execlists_reset(struct intel_engine_cs *engine, bool stalled)
 
 unwind:
 	/* Push back any incomplete requests for replay after the reset. */
+	execlists_cancel_port_requests(execlists);
 	__unwind_incomplete_requests(engine);
 }