iommu/arm-smmu: add support for specifying regulators

On some power-constrained platforms it's useful to disable power when a
device is not in use. Add support for specifying regulators for SMMUs
and only leave power on as long as the SMMU is in use (attached).

Change-Id: I87191d325423f160ddd4b71f5bf3a92f4942b821
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>

Documentation/devicetree/bindings/iommu/arm,smmu.txt

@@ -66,6 +66,9 @@ conditions.
                   Documentation/devicetree/bindings/clock/clock-bindings.txt
                   for more info.
 
+- vdd-supply    : Phandle of the regulator that should be powered on during
+                  SMMU register access.
+
 Example:
 
         smmu {

drivers/iommu/arm-smmu.c

@@ -394,6 +394,11 @@ struct arm_smmu_device {
 
 	int				num_clocks;
 	struct clk			**clocks;
+
+	struct regulator		*gdsc;
+
+	struct mutex			attach_lock;
+	unsigned int			attach_count;
 };
 
 struct arm_smmu_cfg {
@@ -617,6 +622,22 @@ static void arm_smmu_disable_clocks(struct arm_smmu_device *smmu)
 		clk_disable_unprepare(smmu->clocks[i]);
 }
 
+static int arm_smmu_enable_regulators(struct arm_smmu_device *smmu)
+{
+	if (!smmu->gdsc)
+		return 0;
+
+	return regulator_enable(smmu->gdsc);
+}
+
+static int arm_smmu_disable_regulators(struct arm_smmu_device *smmu)
+{
+	if (!smmu->gdsc)
+		return 0;
+
+	return regulator_disable(smmu->gdsc);
+}
+
 /* Wait for any pending TLB invalidations to complete */
 static void arm_smmu_tlb_sync(struct arm_smmu_device *smmu)
 {
@@ -1249,6 +1270,8 @@ static void arm_smmu_domain_remove_master(struct arm_smmu_domain *smmu_domain,
 	arm_smmu_disable_clocks(smmu);
 }
 
+static void arm_smmu_device_reset(struct arm_smmu_device *smmu);
+
 static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 {
 	int ret;
@@ -1267,7 +1290,15 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 		return -EEXIST;
 	}
 
-	arm_smmu_enable_clocks(smmu);
+	mutex_lock(&smmu->attach_lock);
+	if (!smmu->attach_count++) {
+		arm_smmu_enable_regulators(smmu);
+		arm_smmu_enable_clocks(smmu);
+		arm_smmu_device_reset(smmu);
+	} else {
+		arm_smmu_enable_clocks(smmu);
+	}
+	mutex_unlock(&smmu->attach_lock);
 
 	/*
 	 * Sanity check the domain. We don't support domains across
@@ -1278,7 +1309,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 		/* Now that we have a master, we can finalise the domain */
 		ret = arm_smmu_init_domain_context(domain, smmu);
 		if (IS_ERR_VALUE(ret))
-			goto disable_clocks;
+			goto err_disable_clocks;
 
 		dom_smmu = smmu_domain->smmu;
 	}
@@ -1288,28 +1319,46 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 			"cannot attach to SMMU %s whilst already attached to domain on SMMU %s\n",
 			dev_name(smmu_domain->smmu->dev), dev_name(smmu->dev));
 		ret = -EINVAL;
-		goto disable_clocks;
+		goto err_disable_clocks;
 	}
 
 	/* Looks ok, so add the device to the domain */
 	cfg = find_smmu_master_cfg(dev);
 	if (!cfg) {
 		ret = -ENODEV;
-		goto disable_clocks;
+		goto err_disable_clocks;
 	}
 
 	ret = arm_smmu_domain_add_master(smmu_domain, cfg);
 	if (!ret)
 		dev->archdata.iommu = domain;
-disable_clocks:
 	arm_smmu_disable_clocks(smmu);
 	return ret;
+
+err_disable_clocks:
+	arm_smmu_disable_clocks(smmu);
+	mutex_lock(&smmu->attach_lock);
+	if (!--smmu->attach_count)
+		arm_smmu_disable_regulators(smmu);
+	mutex_unlock(&smmu->attach_lock);
+	return ret;
+}
+
+static void arm_smmu_power_off(struct arm_smmu_device *smmu)
+{
+	/* Turn the thing off */
+	arm_smmu_enable_clocks(smmu);
+	writel_relaxed(sCR0_CLIENTPD,
+		ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);
+	arm_smmu_disable_clocks(smmu);
+	arm_smmu_disable_regulators(smmu);
 }
 
 static void arm_smmu_detach_dev(struct iommu_domain *domain, struct device *dev)
 {
 	struct arm_smmu_domain *smmu_domain = domain->priv;
 	struct arm_smmu_master_cfg *cfg;
+	struct arm_smmu_device *smmu = smmu_domain->smmu;
 
 	cfg = find_smmu_master_cfg(dev);
 	if (!cfg)
@@ -1317,6 +1366,10 @@ static void arm_smmu_detach_dev(struct iommu_domain *domain, struct device *dev)
 
 	dev->archdata.iommu = NULL;
 	arm_smmu_domain_remove_master(smmu_domain, cfg);
+	mutex_lock(&smmu->attach_lock);
+	if (!--smmu->attach_count)
+		arm_smmu_power_off(smmu);
+	mutex_unlock(&smmu->attach_lock);
 }
 
 static bool arm_smmu_pte_is_contiguous_range(unsigned long addr,
@@ -1783,6 +1836,20 @@ static int arm_smmu_id_size_to_bits(int size)
 	}
 }
 
+static int arm_smmu_init_regulators(struct arm_smmu_device *smmu)
+{
+	struct device *dev = smmu->dev;
+
+	if (!of_get_property(dev->of_node, "vdd-supply", NULL))
+		return 0;
+
+	smmu->gdsc = devm_regulator_get(dev, "vdd");
+	if (IS_ERR(smmu->gdsc))
+		return PTR_ERR(smmu->gdsc);
+
+	return 0;
+}
+
 static int arm_smmu_init_clocks(struct arm_smmu_device *smmu)
 {
 	const char *cname;
@@ -2008,6 +2075,7 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	}
 	smmu->dev = dev;
+	mutex_init(&smmu->attach_lock);
 
 	of_id = of_match_node(arm_smmu_of_match, dev->of_node);
 	smmu->version = (enum arm_smmu_arch_version)of_id->data;
@@ -2070,15 +2138,21 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
 	}
 	dev_notice(dev, "registered %d master devices\n", i);
 
+	err = arm_smmu_init_regulators(smmu);
+	if (err)
+		goto out_put_masters;
+
 	err = arm_smmu_init_clocks(smmu);
 	if (err)
 		goto out_put_masters;
 
+	arm_smmu_enable_regulators(smmu);
 	arm_smmu_enable_clocks(smmu);
-
 	err = arm_smmu_device_cfg_probe(smmu);
+	arm_smmu_disable_clocks(smmu);
+	arm_smmu_disable_regulators(smmu);
 	if (err)
-		goto out_disable_clocks;
+		goto out_put_masters;
 
 	parse_driver_options(smmu);
 
@@ -2088,7 +2162,7 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
 			"found only %d context interrupt(s) but %d required\n",
 			smmu->num_context_irqs, smmu->num_context_banks);
 		err = -ENODEV;
-		goto out_disable_clocks;
+		goto out_put_masters;
 	}
 
 	for (i = 0; i < smmu->num_global_irqs; ++i) {
@@ -2109,17 +2183,12 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
 	list_add(&smmu->list, &arm_smmu_devices);
 	spin_unlock(&arm_smmu_devices_lock);
 
-	arm_smmu_device_reset(smmu);
-	arm_smmu_disable_clocks(smmu);
 	return 0;
 
 out_free_irqs:
 	while (i--)
 		free_irq(smmu->irqs[i], smmu);
 
-out_disable_clocks:
-	arm_smmu_disable_clocks(smmu);
-
 out_put_masters:
 	for (node = rb_first(&smmu->masters); node; node = rb_next(node)) {
 		struct arm_smmu_master *master
@@ -2162,10 +2231,15 @@ static int arm_smmu_device_remove(struct platform_device *pdev)
 	for (i = 0; i < smmu->num_global_irqs; ++i)
 		free_irq(smmu->irqs[i], smmu);
 
-	/* Turn the thing off */
-	arm_smmu_enable_clocks(smmu);
-	writel(sCR0_CLIENTPD, ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);
-	arm_smmu_disable_clocks(smmu);
+	mutex_lock(&smmu->attach_lock);
+	/*
+	 * If all devices weren't detached for some reason, we're
+	 * still powered on. Power off now.
+	 */
+	if (smmu->attach_count)
+		arm_smmu_power_off(smmu);
+	mutex_unlock(&smmu->attach_lock);
+
 	return 0;
 }