[PATCH] TGL HAX drm/i915/tgl: Interrupts are overrated

[Chris Wilson <chris@chris-wilson.co.uk>]

Why sleep when you can busywait for an interrupt? Throw out the old irq
handlers, and use irq_poll instead.

References: https://bugs.freedesktop.org/show_bug.cgi?id=111880
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
---
 drivers/gpu/drm/i915/Kconfig                 |  1 +
 drivers/gpu/drm/i915/Kconfig.debug           |  5 +++
 drivers/gpu/drm/i915/gt/intel_engine_types.h | 15 ++++++-
 drivers/gpu/drm/i915/gt/intel_gt_irq.c       | 13 ++++--
 drivers/gpu/drm/i915/gt/intel_lrc.c          | 47 ++++++++++++++++++++
 drivers/gpu/drm/i915/i915_drv.h              |  3 ++
 drivers/gpu/drm/i915/i915_irq.c              | 14 +++++-
 drivers/gpu/drm/i915/i915_pci.c              |  1 -
 8 files changed, 90 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 0d21402945ab..bf2b27b6ebf2 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -13,6 +13,7 @@ config DRM_I915
 	select DRM_PANEL
 	select DRM_MIPI_DSI
 	select RELAY
+	select IRQ_POLL
 	select IRQ_WORK
 	# i915 depends on ACPI_VIDEO when ACPI is enabled
 	# but for select to work, need to select ACPI_VIDEO's dependencies, ick
diff --git a/drivers/gpu/drm/i915/Kconfig.debug b/drivers/gpu/drm/i915/Kconfig.debug
index 4a800faa275c..4d23a84ac2c4 100644
--- a/drivers/gpu/drm/i915/Kconfig.debug
+++ b/drivers/gpu/drm/i915/Kconfig.debug
@@ -44,6 +44,7 @@ config DRM_I915_DEBUG
 	select DRM_I915_SELFTEST
 	select DRM_I915_DEBUG_RUNTIME_PM
 	select DRM_I915_DEBUG_MMIO
+	select TIGERLAKE_DEBUG_IRQ
         default n
         help
           Choose this option to turn on extra driver debugging that may affect
@@ -220,3 +221,7 @@ config DRM_I915_DEBUG_RUNTIME_PM
 	  driver loading, suspend and resume operations.
 
 	  If in doubt, say "N"
+
+config TIGERLAKE_DEBUG_IRQ
+	bool "[TGL] Reduce IRQ functionality for stability"
+	default n
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
index 943f0663837e..d3c36e57b888 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
@@ -8,6 +8,7 @@
 #define __INTEL_ENGINE_TYPES__
 
 #include <linux/hashtable.h>
+#include <linux/irq_poll.h>
 #include <linux/irq_work.h>
 #include <linux/kref.h>
 #include <linux/list.h>
@@ -330,6 +331,9 @@ struct intel_engine_cs {
 	struct drm_i915_gem_object *default_state;
 	void *pinned_default_state;
 
+	struct irq_poll irq_poll;
+	atomic_t irq_count;
+
 	struct {
 		struct intel_ring *ring;
 		struct intel_timeline *timeline;
@@ -480,8 +484,9 @@ struct intel_engine_cs {
 #define I915_ENGINE_HAS_PREEMPTION   BIT(2)
 #define I915_ENGINE_HAS_SEMAPHORES   BIT(3)
 #define I915_ENGINE_NEEDS_BREADCRUMB_TASKLET BIT(4)
-#define I915_ENGINE_IS_VIRTUAL       BIT(5)
-#define I915_ENGINE_HAS_RELATIVE_MMIO BIT(6)
+#define I915_ENGINE_NEEDS_IRQ_POLL   BIT(5)
+#define I915_ENGINE_IS_VIRTUAL       BIT(6)
+#define I915_ENGINE_HAS_RELATIVE_MMIO BIT(7)
 	unsigned int flags;
 
 	/*
@@ -571,6 +576,12 @@ intel_engine_needs_breadcrumb_tasklet(const struct intel_engine_cs *engine)
 	return engine->flags & I915_ENGINE_NEEDS_BREADCRUMB_TASKLET;
 }
 
+static inline bool
+intel_engine_needs_irq_poll(const struct intel_engine_cs *engine)
+{
+	return engine->flags & I915_ENGINE_NEEDS_IRQ_POLL;
+}
+
 static inline bool
 intel_engine_is_virtual(const struct intel_engine_cs *engine)
 {
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_irq.c b/drivers/gpu/drm/i915/gt/intel_gt_irq.c
index 34a4fb624bf7..7d4c2f18576e 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_irq.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_irq.c
@@ -45,6 +45,9 @@ gen11_gt_engine_identity(struct intel_gt *gt,
 
 	lockdep_assert_held(&gt->irq_lock);
 
+	if (WARN_ON(TIGERLAKE_NO_IRQ(gt->i915)))
+		return 0;
+
 	raw_reg_write(regs, GEN11_IIR_REG_SELECTOR(bank), BIT(bit));
 
 	/*
@@ -209,12 +212,14 @@ void gen11_gt_irq_reset(struct intel_gt *gt)
 
 void gen11_gt_irq_postinstall(struct intel_gt *gt)
 {
-	const u32 irqs = GT_RENDER_USER_INTERRUPT | GT_CONTEXT_SWITCH_INTERRUPT;
 	struct intel_uncore *uncore = gt->uncore;
-	const u32 dmask = irqs << 16 | irqs;
-	const u32 smask = irqs << 16;
+	u32 irqs, dmask, smask;
 
-	BUILD_BUG_ON(irqs & 0xffff0000);
+	irqs = GT_RENDER_USER_INTERRUPT | GT_CONTEXT_SWITCH_INTERRUPT;
+	if (TIGERLAKE_NO_IRQ(gt->i915))
+		irqs = 0; /* XXX lalalala */
+	smask = irqs << 16;
+	dmask = smask | irqs;
 
 	/* Enable RCS, BCS, VCS and VECS class interrupts. */
 	intel_uncore_write(uncore, GEN11_RENDER_COPY_INTR_ENABLE, dmask);
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 431d3b8c3371..1a785e876a32 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -989,6 +989,9 @@ __execlists_schedule_in(struct i915_request *rq)
 	execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_IN);
 	intel_engine_context_in(engine);
 
+	if (intel_engine_needs_irq_poll(engine))
+		atomic_inc(&engine->irq_count);
+
 	return engine;
 }
 
@@ -1028,6 +1031,10 @@ __execlists_schedule_out(struct i915_request *rq,
 {
 	struct intel_context * const ce = rq->hw_context;
 
+	if (intel_engine_needs_irq_poll(engine) &&
+	    atomic_dec_and_test(&engine->irq_count))
+		set_bit(IRQ_POLL_F_DISABLE, &engine->irq_poll.state);
+
 	intel_engine_context_out(engine);
 	execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_OUT);
 	intel_gt_pm_put(engine->gt);
@@ -1196,6 +1203,11 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
 	/* we need to manually load the submit queue */
 	if (execlists->ctrl_reg)
 		writel(EL_CTRL_LOAD, execlists->ctrl_reg);
+
+	if (atomic_read(&engine->irq_count)) {
+		clear_bit(IRQ_POLL_F_DISABLE, &engine->irq_poll.state);
+		irq_poll_sched(&engine->irq_poll);
+	}
 }
 
 static bool ctx_single_port_submission(const struct intel_context *ce)
@@ -1838,6 +1850,11 @@ gen8_csb_parse(const struct intel_engine_execlists *execlists, const u32 *csb)
 	return *csb & (GEN8_CTX_STATUS_IDLE_ACTIVE | GEN8_CTX_STATUS_PREEMPTED);
 }
 
+static inline bool has_breadcrumbs(struct i915_request *rq)
+{
+	return !list_empty(&rq->hw_context->signals);
+}
+
 static void process_csb(struct intel_engine_cs *engine)
 {
 	struct intel_engine_execlists * const execlists = &engine->execlists;
@@ -1940,6 +1957,10 @@ static void process_csb(struct intel_engine_cs *engine)
 			 */
 			GEM_BUG_ON(!i915_request_completed(*execlists->active) &&
 				   !reset_in_progress(execlists));
+
+			if (has_breadcrumbs(*execlists->active))
+				intel_engine_queue_breadcrumbs(engine);
+
 			execlists_schedule_out(*execlists->active++);
 
 			GEM_BUG_ON(execlists->active - execlists->inflight >
@@ -1987,6 +2008,27 @@ static void execlists_submission_tasklet(unsigned long data)
 	}
 }
 
+static int iop_handler(struct irq_poll *iop, int budget)
+{
+	struct intel_engine_cs *engine =
+		container_of(iop, typeof(*engine), irq_poll);
+	struct intel_engine_execlists *execlists = &engine->execlists;
+	struct tasklet_struct *t = &execlists->tasklet;
+
+	if (execlists->csb_head == READ_ONCE(*execlists->csb_write))
+		return 0;
+
+	if (!tasklet_trylock(t))
+		return 0;
+
+	/* Must wait for any GPU reset in progress. */
+	if (__tasklet_is_enabled(t))
+		t->func(t->data);
+
+	tasklet_unlock(t);
+	return 0;
+}
+
 static void execlists_submission_timer(struct timer_list *timer)
 {
 	struct intel_engine_cs *engine =
@@ -3442,10 +3484,14 @@ void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
 
 	if (engine->class != COPY_ENGINE_CLASS && INTEL_GEN(engine->i915) >= 12)
 		engine->flags |= I915_ENGINE_HAS_RELATIVE_MMIO;
+
+	if (TIGERLAKE_NO_IRQ(engine->i915))
+		engine->flags |= I915_ENGINE_NEEDS_IRQ_POLL;
 }
 
 static void execlists_destroy(struct intel_engine_cs *engine)
 {
+	irq_poll_disable(&engine->irq_poll);
 	intel_engine_cleanup_common(engine);
 	lrc_destroy_wa_ctx(engine);
 	kfree(engine);
@@ -3532,6 +3578,7 @@ static void rcs_submission_override(struct intel_engine_cs *engine)
 
 int intel_execlists_submission_setup(struct intel_engine_cs *engine)
 {
+	irq_poll_init(&engine->irq_poll, -1, iop_handler);
 	tasklet_init(&engine->execlists.tasklet,
 		     execlists_submission_tasklet, (unsigned long)engine);
 	timer_setup(&engine->execlists.timer, execlists_submission_timer, 0);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 337d8306416a..c505d9e38e98 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2069,6 +2069,9 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
 #define IS_GEN9_LP(dev_priv)	(IS_GEN(dev_priv, 9) && IS_LP(dev_priv))
 #define IS_GEN9_BC(dev_priv)	(IS_GEN(dev_priv, 9) && !IS_LP(dev_priv))
 
+#define TIGERLAKE_NO_IRQ(i915) \
+	IS_ENABLED(CONFIG_TIGERLAKE_DEBUG_IRQ) && IS_TIGERLAKE(i915)
+
 #define HAS_ENGINE(dev_priv, id) (INTEL_INFO(dev_priv)->engine_mask & BIT(id))
 
 #define ENGINE_INSTANCES_MASK(dev_priv, first, count) ({		\
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index bc83f094065a..05060f829981 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -360,6 +360,9 @@ void gen6_enable_rps_interrupts(struct drm_i915_private *dev_priv)
 	if (READ_ONCE(rps->interrupts_enabled))
 		return;
 
+	if (!dev_priv->pm_rps_events)
+		return;
+
 	spin_lock_irq(&gt->irq_lock);
 	WARN_ON_ONCE(rps->pm_iir);
 
@@ -376,7 +379,12 @@ void gen6_enable_rps_interrupts(struct drm_i915_private *dev_priv)
 
 u32 gen6_sanitize_rps_pm_mask(const struct drm_i915_private *i915, u32 mask)
 {
-	return mask & ~i915->gt_pm.rps.pm_intrmsk_mbz;
+	const struct intel_rps *rps = &i915->gt_pm.rps;
+
+	if (!rps->interrupts_enabled)
+		return ~0u;
+
+	return mask & ~rps->pm_intrmsk_mbz;
 }
 
 void gen6_disable_rps_interrupts(struct drm_i915_private *dev_priv)
@@ -4314,7 +4322,9 @@ void intel_irq_init(struct drm_i915_private *dev_priv)
 		dev_priv->gt.pm_guc_events = GUC_INTR_GUC2HOST << 16;
 
 	/* Let's track the enabled rps events */
-	if (IS_VALLEYVIEW(dev_priv))
+	if (TIGERLAKE_NO_IRQ(dev_priv))
+		dev_priv->pm_rps_events = 0;
+	else if (IS_VALLEYVIEW(dev_priv))
 		/* WaGsvRC0ResidencyMethod:vlv */
 		dev_priv->pm_rps_events = GEN6_PM_RP_UP_EI_EXPIRED;
 	else
diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
index 1cbf3998b361..86be10cc6a70 100644
--- a/drivers/gpu/drm/i915/i915_pci.c
+++ b/drivers/gpu/drm/i915/i915_pci.c
@@ -806,7 +806,6 @@ static const struct intel_device_info intel_tigerlake_12_info = {
 	.display.has_modular_fia = 1,
 	.engine_mask =
 		BIT(RCS0) | BIT(BCS0) | BIT(VECS0) | BIT(VCS0) | BIT(VCS2),
-	.has_rps = false, /* XXX disabled for debugging */
 };
 
 #undef GEN
-- 
2.23.0

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