drm/i915/execlists: Drop clear_gtiir() on GPU reset

With the new CSB processing code, we are not vulnerable to delayed
delivery of a pre-reset interrupt as we use the CSB status pointers in
the HWSP to decide if we need to parse any CSB events and no longer need
to wait for the first post-reset interrupt to be assured that the CSB
mmio registers are valid.

The new icl code to clear registers has a nasty lock inversion:
[   57.409776] ======================================================
[   57.409779] WARNING: possible circular locking dependency detected
[   57.409783] 4.18.0-rc4-CI-CI_DII_1137+ #1 Tainted: G     U  W
[   57.409785] ------------------------------------------------------
[   57.409788] swapper/6/0 is trying to acquire lock:
[   57.409790] 000000004f304ee5 (&engine->timeline.lock/1){-.-.}, at: execlists_submit_request+0x2b/0x1a0 [i915]
[   57.409841]
               but task is already holding lock:
[   57.409844] 00000000aad89594 (&(&rq->lock)->rlock#2){-.-.}, at: notify_ring+0x2b2/0x480 [i915]
[   57.409869]
               which lock already depends on the new lock.

[   57.409872]
               the existing dependency chain (in reverse order) is:
[   57.409876]
               -> #2 (&(&rq->lock)->rlock#2){-.-.}:
[   57.409900]        notify_ring+0x2b2/0x480 [i915]
[   57.409922]        gen8_cs_irq_handler+0x39/0xa0 [i915]
[   57.409943]        gen11_irq_handler+0x2f0/0x420 [i915]
[   57.409949]        __handle_irq_event_percpu+0x42/0x370
[   57.409952]        handle_irq_event_percpu+0x2b/0x70
[   57.409956]        handle_irq_event+0x2f/0x50
[   57.409959]        handle_edge_irq+0xe7/0x190
[   57.409964]        handle_irq+0x67/0x160
[   57.409967]        do_IRQ+0x5e/0x120
[   57.409971]        ret_from_intr+0x0/0x1d
[   57.409974]        _raw_spin_unlock_irqrestore+0x4e/0x60
[   57.409979]        tasklet_action_common.isra.5+0x47/0xb0
[   57.409982]        __do_softirq+0xd9/0x505
[   57.409985]        irq_exit+0xa9/0xc0
[   57.409988]        do_IRQ+0x9a/0x120
[   57.409991]        ret_from_intr+0x0/0x1d
[   57.409995]        cpuidle_enter_state+0xac/0x360
[   57.409999]        do_idle+0x1f3/0x250
[   57.410004]        cpu_startup_entry+0x6a/0x70
[   57.410010]        start_secondary+0x19d/0x1f0
[   57.410015]        secondary_startup_64+0xa5/0xb0
[   57.410018]
               -> #1 (&(&dev_priv->irq_lock)->rlock){-.-.}:
[   57.410081]        clear_gtiir+0x30/0x200 [i915]
[   57.410116]        execlists_reset+0x6e/0x2b0 [i915]
[   57.410140]        i915_reset_engine+0x111/0x190 [i915]
[   57.410165]        i915_handle_error+0x11a/0x4a0 [i915]
[   57.410198]        i915_hangcheck_elapsed+0x378/0x530 [i915]
[   57.410204]        process_one_work+0x248/0x6c0
[   57.410207]        worker_thread+0x37/0x380
[   57.410211]        kthread+0x119/0x130
[   57.410215]        ret_from_fork+0x3a/0x50
[   57.410217]
               -> #0 (&engine->timeline.lock/1){-.-.}:
[   57.410224]        _raw_spin_lock_irqsave+0x33/0x50
[   57.410256]        execlists_submit_request+0x2b/0x1a0 [i915]
[   57.410289]        submit_notify+0x8d/0x124 [i915]
[   57.410314]        __i915_sw_fence_complete+0x81/0x250 [i915]
[   57.410339]        dma_i915_sw_fence_wake+0xd/0x20 [i915]
[   57.410344]        dma_fence_signal_locked+0x79/0x200
[   57.410368]        notify_ring+0x2ba/0x480 [i915]
[   57.410392]        gen8_cs_irq_handler+0x39/0xa0 [i915]
[   57.410416]        gen11_irq_handler+0x2f0/0x420 [i915]
[   57.410421]        __handle_irq_event_percpu+0x42/0x370
[   57.410425]        handle_irq_event_percpu+0x2b/0x70
[   57.410428]        handle_irq_event+0x2f/0x50
[   57.410432]        handle_edge_irq+0xe7/0x190
[   57.410436]        handle_irq+0x67/0x160
[   57.410439]        do_IRQ+0x5e/0x120
[   57.410445]        ret_from_intr+0x0/0x1d
[   57.410449]        cpuidle_enter_state+0xac/0x360
[   57.410453]        do_idle+0x1f3/0x250
[   57.410456]        cpu_startup_entry+0x6a/0x70
[   57.410460]        start_secondary+0x19d/0x1f0
[   57.410464]        secondary_startup_64+0xa5/0xb0
[   57.410466]
               other info that might help us debug this:

[   57.410471] Chain exists of:
                 &engine->timeline.lock/1 --> &(&dev_priv->irq_lock)->rlock --> &(&rq->lock)->rlock#2

[   57.410481]  Possible unsafe locking scenario:

[   57.410485]        CPU0                    CPU1
[   57.410487]        ----                    ----
[   57.410490]   lock(&(&rq->lock)->rlock#2);
[   57.410494]                                lock(&(&dev_priv->irq_lock)->rlock);
[   57.410498]                                lock(&(&rq->lock)->rlock#2);
[   57.410503]   lock(&engine->timeline.lock/1);
[   57.410506]
                *** DEADLOCK ***

[   57.410511] 4 locks held by swapper/6/0:
[   57.410514]  #0: 0000000074575789 (&(&dev_priv->irq_lock)->rlock){-.-.}, at: gen11_irq_handler+0x8a/0x420 [i915]
[   57.410542]  #1: 000000009b29b30e (rcu_read_lock){....}, at: notify_ring+0x1a/0x480 [i915]
[   57.410573]  #2: 00000000aad89594 (&(&rq->lock)->rlock#2){-.-.}, at: notify_ring+0x2b2/0x480 [i915]
[   57.410601]  #3: 000000009b29b30e (rcu_read_lock){....}, at: submit_notify+0x35/0x124 [i915]
[   57.410635]
               stack backtrace:
[   57.410640] CPU: 6 PID: 0 Comm: swapper/6 Tainted: G     U  W         4.18.0-rc4-CI-CI_DII_1137+ #1
[   57.410644] Hardware name: Intel Corporation Ice Lake Client Platform/IceLake U DDR4 SODIMM PD RVP, BIOS ICLSFWR1.R00.2222.A01.1805300339 05/30/2018
[   57.410650] Call Trace:
[   57.410652]  <IRQ>
[   57.410657]  dump_stack+0x67/0x9b
[   57.410662]  print_circular_bug.isra.16+0x1c8/0x2b0
[   57.410666]  __lock_acquire+0x1897/0x1b50
[   57.410671]  ? lock_acquire+0xa6/0x210
[   57.410674]  lock_acquire+0xa6/0x210
[   57.410706]  ? execlists_submit_request+0x2b/0x1a0 [i915]
[   57.410711]  _raw_spin_lock_irqsave+0x33/0x50
[   57.410741]  ? execlists_submit_request+0x2b/0x1a0 [i915]
[   57.410769]  execlists_submit_request+0x2b/0x1a0 [i915]
[   57.410774]  ? _raw_spin_unlock_irqrestore+0x39/0x60
[   57.410804]  submit_notify+0x8d/0x124 [i915]
[   57.410828]  __i915_sw_fence_complete+0x81/0x250 [i915]
[   57.410854]  dma_i915_sw_fence_wake+0xd/0x20 [i915]
[   57.410858]  dma_fence_signal_locked+0x79/0x200
[   57.410882]  notify_ring+0x2ba/0x480 [i915]
[   57.410907]  gen8_cs_irq_handler+0x39/0xa0 [i915]
[   57.410933]  gen11_irq_handler+0x2f0/0x420 [i915]
[   57.410938]  __handle_irq_event_percpu+0x42/0x370
[   57.410943]  handle_irq_event_percpu+0x2b/0x70
[   57.410947]  handle_irq_event+0x2f/0x50
[   57.410951]  handle_edge_irq+0xe7/0x190
[   57.410955]  handle_irq+0x67/0x160
[   57.410958]  do_IRQ+0x5e/0x120
[   57.410962]  common_interrupt+0xf/0xf
[   57.410965]  </IRQ>
[   57.410969] RIP: 0010:cpuidle_enter_state+0xac/0x360
[   57.410972] Code: 44 00 00 31 ff e8 84 93 91 ff 45 84 f6 74 12 9c 58 f6 c4 02 0f 85 31 02 00 00 31 ff e8 7d 30 98 ff e8 e8 0e 94 ff fb 4c 29 fb <48> ba cf f7 53 e3 a5 9b c4 20 48 89 d8 48 c1 fb 3f 48 f7 ea b8 ff
[   57.411015] RSP: 0018:ffffc90000133e90 EFLAGS: 00000216 ORIG_RAX: ffffffffffffffdd
[   57.411023] RAX: ffff8804ae748040 RBX: 000000000002a97d RCX: 0000000000000000
[   57.411029] RDX: 0000000000000046 RSI: ffffffff82141263 RDI: ffffffff820f05a7
[   57.411035] RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
[   57.411041] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff8229f078
[   57.411045] R13: ffff8804ab2adfa8 R14: 0000000000000000 R15: 0000000d5de092e3
[   57.411052]  do_idle+0x1f3/0x250
[   57.411055]  cpu_startup_entry+0x6a/0x70
[   57.411059]  start_secondary+0x19d/0x1f0
[   57.411064]  secondary_startup_64+0xa5/0xb0

The easiest remedy is to remove the defunct code.

Fixes: ff047a87 ("drm/i915/icl: Correctly clear lost ctx-switch interrupts across reset for Gen11")
References: fd8526e5 ("drm/i915/execlists: Trust the CSB")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180713203529.1973-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_irq.c

@@ -263,9 +263,9 @@ static u32
 gen11_gt_engine_identity(struct drm_i915_private * const i915,
 			 const unsigned int bank, const unsigned int bit);
 
-bool gen11_reset_one_iir(struct drm_i915_private * const i915,
-			 const unsigned int bank,
-			 const unsigned int bit)
+static bool gen11_reset_one_iir(struct drm_i915_private * const i915,
+				const unsigned int bank,
+				const unsigned int bit)
 {
 	void __iomem * const regs = i915->regs;
 	u32 dw;

drivers/gpu/drm/i915/intel_drv.h

@@ -1353,9 +1353,6 @@ void intel_check_cpu_fifo_underruns(struct drm_i915_private *dev_priv);
 void intel_check_pch_fifo_underruns(struct drm_i915_private *dev_priv);
 
 /* i915_irq.c */
-bool gen11_reset_one_iir(struct drm_i915_private * const i915,
-			 const unsigned int bank,
-			 const unsigned int bit);
 void gen5_enable_gt_irq(struct drm_i915_private *dev_priv, uint32_t mask);
 void gen5_disable_gt_irq(struct drm_i915_private *dev_priv, uint32_t mask);
 void gen6_mask_pm_irq(struct drm_i915_private *dev_priv, u32 mask);

drivers/gpu/drm/i915/intel_lrc.c

@@ -796,72 +796,6 @@ execlists_cancel_port_requests(struct intel_engine_execlists * const execlists)
 	execlists_user_end(execlists);
 }
 
-static void clear_gtiir(struct intel_engine_cs *engine)
-{
-	struct drm_i915_private *dev_priv = engine->i915;
-	int i;
-
-	/*
-	 * Clear any pending interrupt state.
-	 *
-	 * We do it twice out of paranoia that some of the IIR are
-	 * double buffered, and so if we only reset it once there may
-	 * still be an interrupt pending.
-	 */
-	if (INTEL_GEN(dev_priv) >= 11) {
-		static const struct {
-			u8 bank;
-			u8 bit;
-		} gen11_gtiir[] = {
-			[RCS] = {0, GEN11_RCS0},
-			[BCS] = {0, GEN11_BCS},
-			[_VCS(0)] = {1, GEN11_VCS(0)},
-			[_VCS(1)] = {1, GEN11_VCS(1)},
-			[_VCS(2)] = {1, GEN11_VCS(2)},
-			[_VCS(3)] = {1, GEN11_VCS(3)},
-			[_VECS(0)] = {1, GEN11_VECS(0)},
-			[_VECS(1)] = {1, GEN11_VECS(1)},
-		};
-		unsigned long irqflags;
-
-		GEM_BUG_ON(engine->id >= ARRAY_SIZE(gen11_gtiir));
-
-		spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
-		for (i = 0; i < 2; i++) {
-			gen11_reset_one_iir(dev_priv,
-					    gen11_gtiir[engine->id].bank,
-					    gen11_gtiir[engine->id].bit);
-		}
-		spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
-	} else {
-		static const u8 gtiir[] = {
-			[RCS]  = 0,
-			[BCS]  = 0,
-			[VCS]  = 1,
-			[VCS2] = 1,
-			[VECS] = 3,
-		};
-
-		GEM_BUG_ON(engine->id >= ARRAY_SIZE(gtiir));
-
-		for (i = 0; i < 2; i++) {
-			I915_WRITE(GEN8_GT_IIR(gtiir[engine->id]),
-				   engine->irq_keep_mask);
-			POSTING_READ(GEN8_GT_IIR(gtiir[engine->id]));
-		}
-		GEM_BUG_ON(I915_READ(GEN8_GT_IIR(gtiir[engine->id])) &
-			   engine->irq_keep_mask);
-	}
-}
-
-static void reset_irq(struct intel_engine_cs *engine)
-{
-	/* Mark all CS interrupts as complete */
-	smp_store_mb(engine->execlists.active, 0);
-
-	clear_gtiir(engine);
-}
-
 static void reset_csb_pointers(struct intel_engine_execlists *execlists)
 {
 	/*
@@ -905,7 +839,6 @@ static void execlists_cancel_requests(struct intel_engine_cs *engine)
 
 	/* Cancel the requests on the HW and clear the ELSP tracker. */
 	execlists_cancel_port_requests(execlists);
-	reset_irq(engine);
 
 	/* Mark all executing requests as skipped. */
 	list_for_each_entry(rq, &engine->timeline.requests, link) {
@@ -1976,7 +1909,6 @@ static void execlists_reset(struct intel_engine_cs *engine,
 	 * requests were completed.
 	 */
 	execlists_cancel_port_requests(execlists);
-	reset_irq(engine);
 
 	/* Push back any incomplete requests for replay after the reset. */
 	__unwind_incomplete_requests(engine);