drm/i915: Track hw reported context runtime

GPU saves accumulated context runtime (in CS timestamp units) in PPHWSP
which will be useful for us in cases when we are not able to track context
busyness ourselves (like with GuC). Keep a copy of this in struct
intel_context from where it can be easily read even if the context is not
pinned.

v2:
 (Chris)
 * Do not store pphwsp address in intel_context.
 * Log CS wrap-around.
 * Simplify calculation by relying on integer wraparound.
v3:
 * Include total/avg in traces and error state for debugging

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200216133620.394962-1-chris@chris-wilson.co.uk

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

@@ -220,7 +220,9 @@ static void __intel_context_retire(struct i915_active *active)
 {
 	struct intel_context *ce = container_of(active, typeof(*ce), active);
 
-	CE_TRACE(ce, "retire\n");
+	CE_TRACE(ce, "retire runtime: { total:%lluns, avg:%lluns }\n",
+		 intel_context_get_total_runtime_ns(ce),
+		 intel_context_get_avg_runtime_ns(ce));
 
 	set_bit(CONTEXT_VALID_BIT, &ce->flags);
 	if (ce->state)
@@ -281,6 +283,8 @@ intel_context_init(struct intel_context *ce,
 	ce->sseu = engine->sseu;
 	ce->ring = __intel_context_ring_size(SZ_4K);
 
+	ewma_runtime_init(&ce->runtime.avg);
+
 	ce->vm = i915_vm_get(engine->gt->vm);
 
 	INIT_LIST_HEAD(&ce->signal_link);

drivers/gpu/drm/i915/gt/intel_context.h

@@ -12,6 +12,7 @@
 #include <linux/types.h>
 
 #include "i915_active.h"
+#include "i915_drv.h"
 #include "intel_context_types.h"
 #include "intel_engine_types.h"
 #include "intel_ring_types.h"
@@ -227,4 +228,20 @@ intel_context_clear_nopreempt(struct intel_context *ce)
 	clear_bit(CONTEXT_NOPREEMPT, &ce->flags);
 }
 
+static inline u64 intel_context_get_total_runtime_ns(struct intel_context *ce)
+{
+	const u32 period =
+		RUNTIME_INFO(ce->engine->i915)->cs_timestamp_period_ns;
+
+	return READ_ONCE(ce->runtime.total) * period;
+}
+
+static inline u64 intel_context_get_avg_runtime_ns(struct intel_context *ce)
+{
+	const u32 period =
+		RUNTIME_INFO(ce->engine->i915)->cs_timestamp_period_ns;
+
+	return mul_u32_u32(ewma_runtime_read(&ce->runtime.avg), period);
+}
+
 #endif /* __INTEL_CONTEXT_H__ */

drivers/gpu/drm/i915/gt/intel_context_types.h

@@ -7,6 +7,7 @@
 #ifndef __INTEL_CONTEXT_TYPES__
 #define __INTEL_CONTEXT_TYPES__
 
+#include <linux/average.h>
 #include <linux/kref.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
@@ -19,6 +20,8 @@
 
 #define CONTEXT_REDZONE POISON_INUSE
 
+DECLARE_EWMA(runtime, 3, 8);
+
 struct i915_gem_context;
 struct i915_vma;
 struct intel_context;
@@ -68,6 +71,15 @@ struct intel_context {
 	u64 lrc_desc;
 	u32 tag; /* cookie passed to HW to track this context on submission */
 
+	/* Time on GPU as tracked by the hw. */
+	struct {
+		struct ewma_runtime avg;
+		u64 total;
+		u32 last;
+		I915_SELFTEST_DECLARE(u32 num_underflow);
+		I915_SELFTEST_DECLARE(u32 max_underflow);
+	} runtime;
+
 	unsigned int active_count; /* protected by timeline->mutex */
 
 	atomic_t pin_count;

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

@@ -1195,6 +1195,42 @@ static void reset_active(struct i915_request *rq,
 	ce->lrc_desc |= CTX_DESC_FORCE_RESTORE;
 }
 
+static u32 intel_context_get_runtime(const struct intel_context *ce)
+{
+	/*
+	 * We can use either ppHWSP[16] which is recorded before the context
+	 * switch (and so excludes the cost of context switches) or use the
+	 * value from the context image itself, which is saved/restored earlier
+	 * and so includes the cost of the save.
+	 */
+	return READ_ONCE(ce->lrc_reg_state[CTX_TIMESTAMP]);
+}
+
+static void intel_context_update_runtime(struct intel_context *ce)
+{
+	u32 old;
+	s32 dt;
+
+	if (intel_context_is_barrier(ce))
+		return;
+
+	old = ce->runtime.last;
+	ce->runtime.last = intel_context_get_runtime(ce);
+	dt = ce->runtime.last - old;
+
+	if (unlikely(dt <= 0)) {
+		CE_TRACE(ce, "runtime underflow: last=%u, new=%u, delta=%d\n",
+			 old, ce->runtime.last, dt);
+		I915_SELFTEST_ONLY(ce->runtime.num_underflow += dt < 0);
+		I915_SELFTEST_ONLY(ce->runtime.max_underflow =
+				   max_t(u32, ce->runtime.max_underflow, -dt));
+		return;
+	}
+
+	ewma_runtime_add(&ce->runtime.avg, dt);
+	ce->runtime.total += dt;
+}
+
 static inline struct intel_engine_cs *
 __execlists_schedule_in(struct i915_request *rq)
 {
@@ -1278,6 +1314,7 @@ __execlists_schedule_out(struct i915_request *rq,
 	    i915_request_completed(rq))
 		intel_engine_add_retire(engine, ce->timeline);
 
+	intel_context_update_runtime(ce);
 	intel_engine_context_out(engine);
 	execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_OUT);
 	intel_gt_pm_put_async(engine->gt);
@@ -4607,8 +4644,13 @@ populate_lr_context(struct intel_context *ce,
 		inhibit = false;
 	}
 
-	/* The second page of the context object contains some fields which must
-	 * be set up prior to the first execution. */
+	/* Clear the ppHWSP (inc. per-context counters) */
+	memset(vaddr, 0, PAGE_SIZE);
+
+	/*
+	 * The second page of the context object contains some registers which
+	 * must be set up prior to the first execution.
+	 */
 	execlists_init_reg_state(vaddr + LRC_STATE_PN * PAGE_SIZE,
 				 ce, engine, ring, inhibit);
 

drivers/gpu/drm/i915/gt/intel_lrc_reg.h

@@ -17,6 +17,7 @@
 #define CTX_RING_CTL			(0x0a + 1)
 #define CTX_BB_STATE			(0x10 + 1)
 #define CTX_BB_PER_CTX_PTR		(0x18 + 1)
+#define CTX_TIMESTAMP			(0x22 + 1)
 #define CTX_PDP3_UDW			(0x24 + 1)
 #define CTX_PDP3_LDW			(0x26 + 1)
 #define CTX_PDP2_UDW			(0x28 + 1)

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

@@ -4151,6 +4151,11 @@ static int live_lrc_fixed(void *arg)
 				CTX_BB_STATE - 1,
 				"BB_STATE"
 			},
+			{
+				i915_mmio_reg_offset(RING_CTX_TIMESTAMP(engine->mmio_base)),
+				CTX_TIMESTAMP - 1,
+				"RING_CTX_TIMESTAMP"
+			},
 			{ },
 		}, *t;
 		u32 *hw;
@@ -4450,6 +4455,96 @@ static int live_gpr_clear(void *arg)
 	return err;
 }
 
+static int __live_pphwsp_runtime(struct intel_engine_cs *engine)
+{
+	struct intel_context *ce;
+	struct i915_request *rq;
+	IGT_TIMEOUT(end_time);
+	int err;
+
+	ce = intel_context_create(engine);
+	if (IS_ERR(ce))
+		return PTR_ERR(ce);
+
+	ce->runtime.num_underflow = 0;
+	ce->runtime.max_underflow = 0;
+
+	do {
+		unsigned int loop = 1024;
+
+		while (loop) {
+			rq = intel_context_create_request(ce);
+			if (IS_ERR(rq)) {
+				err = PTR_ERR(rq);
+				goto err_rq;
+			}
+
+			if (--loop == 0)
+				i915_request_get(rq);
+
+			i915_request_add(rq);
+		}
+
+		if (__igt_timeout(end_time, NULL))
+			break;
+
+		i915_request_put(rq);
+	} while (1);
+
+	err = i915_request_wait(rq, 0, HZ / 5);
+	if (err < 0) {
+		pr_err("%s: request not completed!\n", engine->name);
+		goto err_wait;
+	}
+
+	igt_flush_test(engine->i915);
+
+	pr_info("%s: pphwsp runtime %lluns, average %lluns\n",
+		engine->name,
+		intel_context_get_total_runtime_ns(ce),
+		intel_context_get_avg_runtime_ns(ce));
+
+	err = 0;
+	if (ce->runtime.num_underflow) {
+		pr_err("%s: pphwsp underflow %u time(s), max %u cycles!\n",
+		       engine->name,
+		       ce->runtime.num_underflow,
+		       ce->runtime.max_underflow);
+		GEM_TRACE_DUMP();
+		err = -EOVERFLOW;
+	}
+
+err_wait:
+	i915_request_put(rq);
+err_rq:
+	intel_context_put(ce);
+	return err;
+}
+
+static int live_pphwsp_runtime(void *arg)
+{
+	struct intel_gt *gt = arg;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	int err = 0;
+
+	/*
+	 * Check that cumulative context runtime as stored in the pphwsp[16]
+	 * is monotonic.
+	 */
+
+	for_each_engine(engine, gt, id) {
+		err = __live_pphwsp_runtime(engine);
+		if (err)
+			break;
+	}
+
+	if (igt_flush_test(gt->i915))
+		err = -EIO;
+
+	return err;
+}
+
 int intel_lrc_live_selftests(struct drm_i915_private *i915)
 {
 	static const struct i915_subtest tests[] = {
@@ -4457,6 +4552,7 @@ int intel_lrc_live_selftests(struct drm_i915_private *i915)
 		SUBTEST(live_lrc_fixed),
 		SUBTEST(live_lrc_state),
 		SUBTEST(live_gpr_clear),
+		SUBTEST(live_pphwsp_runtime),
 	};
 
 	if (!HAS_LOGICAL_RING_CONTEXTS(i915))

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -481,9 +481,13 @@ static void error_print_context(struct drm_i915_error_state_buf *m,
 				const char *header,
 				const struct i915_gem_context_coredump *ctx)
 {
-	err_printf(m, "%s%s[%d] prio %d, guilty %d active %d\n",
+	const u32 period = RUNTIME_INFO(m->i915)->cs_timestamp_period_ns;
+
+	err_printf(m, "%s%s[%d] prio %d, guilty %d active %d, runtime total %lluns, avg %lluns\n",
 		   header, ctx->comm, ctx->pid, ctx->sched_attr.priority,
-		   ctx->guilty, ctx->active);
+		   ctx->guilty, ctx->active,
+		   ctx->total_runtime * period,
+		   mul_u32_u32(ctx->avg_runtime, period));
 }
 
 static struct i915_vma_coredump *
@@ -1260,6 +1264,9 @@ static bool record_context(struct i915_gem_context_coredump *e,
 	e->guilty = atomic_read(&ctx->guilty_count);
 	e->active = atomic_read(&ctx->active_count);
 
+	e->total_runtime = rq->context->runtime.total;
+	e->avg_runtime = ewma_runtime_read(&rq->context->runtime.avg);
+
 	simulated = i915_gem_context_no_error_capture(ctx);
 
 	i915_gem_context_put(ctx);

drivers/gpu/drm/i915/i915_gpu_error.h

@@ -88,6 +88,10 @@ struct intel_engine_coredump {
 
 	struct i915_gem_context_coredump {
 		char comm[TASK_COMM_LEN];
+
+		u64 total_runtime;
+		u32 avg_runtime;
+
 		pid_t pid;
 		int active;
 		int guilty;

drivers/gpu/drm/i915/intel_device_info.c

@@ -1045,6 +1045,12 @@ void intel_device_info_runtime_init(struct drm_i915_private *dev_priv)
 
 	/* Initialize command stream timestamp frequency */
 	runtime->cs_timestamp_frequency_khz = read_timestamp_frequency(dev_priv);
+	runtime->cs_timestamp_period_ns =
+		div_u64(1e6, runtime->cs_timestamp_frequency_khz);
+	drm_dbg(&dev_priv->drm,
+		"CS timestamp wraparound in %lldms\n",
+		div_u64(mul_u32_u32(runtime->cs_timestamp_period_ns, S32_MAX),
+			USEC_PER_SEC));
 }
 
 void intel_driver_caps_print(const struct intel_driver_caps *caps,

drivers/gpu/drm/i915/intel_device_info.h

@@ -217,6 +217,7 @@ struct intel_runtime_info {
 	struct sseu_dev_info sseu;
 
 	u32 cs_timestamp_frequency_khz;
+	u32 cs_timestamp_period_ns;
 
 	/* Media engine access to SFC per instance */
 	u8 vdbox_sfc_access;