drm/i915/selftests: add test to verify get/put fw domains

Exercise acquiring and releasing forcewake around register reads. In
order to read a register behind a GT powerwell, we need to instruct that
powerwell to wake up using a forcewake. When we no longer require the GT
powerwell, we tell the GT to release our forcewake. Inside the
forcewake, the register read should work but outside it should just
return garbage, 0 being the most common garbage. Thus we can detect when
we are inside and outside of the forcewake with just a simple register
read, and so can verify that the GT powerwell is released when we say
so.

v2: Picking the right forcewaked register to return 0 outside of
forcewake is an art.
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@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/20190320080052.27273-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/selftests/intel_uncore.c

@@ -119,9 +119,130 @@ int intel_uncore_mock_selftests(void)
 	return 0;
 }
 
-static int intel_uncore_check_forcewake_domains(struct drm_i915_private *dev_priv)
+static int live_forcewake_ops(void *arg)
+{
+	static const struct reg {
+		const char *name;
+		unsigned long platforms;
+		unsigned int offset;
+	} registers[] = {
+		{
+			"RING_START",
+			INTEL_GEN_MASK(6, 7),
+			0x38,
+		},
+		{
+			"RING_MI_MODE",
+			INTEL_GEN_MASK(8, BITS_PER_LONG),
+			0x9c,
+		}
+	};
+	const struct reg *r;
+	struct drm_i915_private *i915 = arg;
+	struct intel_uncore_forcewake_domain *domain;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	intel_wakeref_t wakeref;
+	unsigned int tmp;
+	int err = 0;
+
+	GEM_BUG_ON(i915->gt.awake);
+
+	/* vlv/chv with their pcu behave differently wrt reads */
+	if (IS_VALLEYVIEW(i915) || IS_CHERRYVIEW(i915)) {
+		pr_debug("PCU fakes forcewake badly; skipping\n");
+		return 0;
+	}
+
+	/* We have to pick carefully to get the exact behaviour we need */
+	for (r = registers; r->name; r++)
+		if (r->platforms & INTEL_INFO(i915)->gen_mask)
+			break;
+	if (!r->name) {
+		pr_debug("Forcewaked register not known for %s; skipping\n",
+			 intel_platform_name(INTEL_INFO(i915)->platform));
+		return 0;
+	}
+
+	wakeref = intel_runtime_pm_get(i915);
+
+	for_each_fw_domain(domain, i915, tmp) {
+		smp_store_mb(domain->active, false);
+		if (!hrtimer_cancel(&domain->timer))
+			continue;
+
+		intel_uncore_fw_release_timer(&domain->timer);
+	}
+
+	for_each_engine(engine, i915, id) {
+		i915_reg_t mmio = _MMIO(engine->mmio_base + r->offset);
+		u32 __iomem *reg = i915->regs + engine->mmio_base + r->offset;
+		enum forcewake_domains fw_domains;
+		u32 val;
+
+		if (!engine->default_state)
+			continue;
+
+		fw_domains = intel_uncore_forcewake_for_reg(i915, mmio,
+							    FW_REG_READ);
+		if (!fw_domains)
+			continue;
+
+		for_each_fw_domain_masked(domain, fw_domains, i915, tmp) {
+			if (!domain->wake_count)
+				continue;
+
+			pr_err("fw_domain %s still active, aborting test!\n",
+			       intel_uncore_forcewake_domain_to_str(domain->id));
+			err = -EINVAL;
+			goto out_rpm;
+		}
+
+		intel_uncore_forcewake_get(i915, fw_domains);
+		val = readl(reg);
+		intel_uncore_forcewake_put(i915, fw_domains);
+
+		/* Flush the forcewake release (delayed onto a timer) */
+		for_each_fw_domain_masked(domain, fw_domains, i915, tmp) {
+			smp_store_mb(domain->active, false);
+			if (hrtimer_cancel(&domain->timer))
+				intel_uncore_fw_release_timer(&domain->timer);
+
+			preempt_disable();
+			err = wait_ack_clear(domain, FORCEWAKE_KERNEL);
+			preempt_enable();
+			if (err) {
+				pr_err("Failed to clear fw_domain %s\n",
+				       intel_uncore_forcewake_domain_to_str(domain->id));
+				goto out_rpm;
+			}
+		}
+
+		if (!val) {
+			pr_err("%s:%s was zero while fw was held!\n",
+			       engine->name, r->name);
+			err = -EINVAL;
+			goto out_rpm;
+		}
+
+		/* We then expect the read to return 0 outside of the fw */
+		if (wait_for(readl(reg) == 0, 100)) {
+			pr_err("%s:%s=%0x, fw_domains 0x%x still up after 100ms!\n",
+			       engine->name, r->name, readl(reg), fw_domains);
+			err = -ETIMEDOUT;
+			goto out_rpm;
+		}
+	}
+
+out_rpm:
+	intel_runtime_pm_put(i915, wakeref);
+	return err;
+}
+
+static int live_forcewake_domains(void *arg)
 {
 #define FW_RANGE 0x40000
+	struct drm_i915_private *dev_priv = arg;
 	unsigned long *valid;
 	u32 offset;
 	int err;
@@ -179,6 +300,11 @@ static int intel_uncore_check_forcewake_domains(struct drm_i915_private *dev_pri
 
 int intel_uncore_live_selftests(struct drm_i915_private *i915)
 {
+	static const struct i915_subtest tests[] = {
+		SUBTEST(live_forcewake_ops),
+		SUBTEST(live_forcewake_domains),
+	};
+
 	int err;
 
 	/* Confirm the table we load is still valid */
@@ -188,9 +314,5 @@ int intel_uncore_live_selftests(struct drm_i915_private *i915)
 	if (err)
 		return err;
 
-	err = intel_uncore_check_forcewake_domains(i915);
-	if (err)
-		return err;
-
-	return 0;
+	return i915_subtests(tests, i915);
 }