[PATCH 4/7] xen/arm: SMMU: Detect types of device tree binding

[Wei Chen <Wei.Chen@arm.com>]

The device tree provides two types of IOMMU bindings, one is legacy
another is generic. The legacy bindings will be depercated in favour
of the generic bindings. But in the transitional period, we have to
support both of them.

The codes to handle these two types of bindings are very differnet,
so we have to detect the binding types while doing SMMU probing.

This detect code is based on Linux ARM SMMUv2 driver:
https://github.com/torvalds/linux/blob/master/drivers/iommu/arm-smmu.c

Signed-off-by: Wei Chen <Wei.Chen@arm.com>
---
 xen/drivers/passthrough/arm/smmu.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/xen/drivers/passthrough/arm/smmu.c b/xen/drivers/passthrough/arm/smmu.c
index 2efa52d..441c296 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -143,6 +143,8 @@ typedef enum irqreturn irqreturn_t;
 
 #define dev_name(dev) dt_node_full_name(dev_to_dt(dev))
 
+#define pr_notice(fmt, ...) printk(XENLOG_INFO fmt, ## __VA_ARGS__)
+
 /* Alias to Xen allocation helpers */
 #define kfree xfree
 #define kmalloc(size, flags)		_xmalloc(size, sizeof(void *))
@@ -681,6 +683,8 @@ struct arm_smmu_option_prop {
 	const char *prop;
 };
 
+static bool using_legacy_binding, using_generic_binding;
+
 static struct arm_smmu_option_prop arm_smmu_options[] = {
 	{ ARM_SMMU_OPT_SECURE_CFG_ACCESS, "calxeda,smmu-secure-config-access" },
 	{ 0, NULL},
@@ -2289,6 +2293,25 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
 	struct rb_node *node;
 	struct of_phandle_args masterspec;
 	int num_irqs, i, err;
+	bool legacy_binding;
+
+	/*
+	 * Xen: Do the same check as Linux. Checking the SMMU device tree bindings
+	 * are either using generic or legacy one.
+	 *
+	 * The "mmu-masters" property is only existed in legacy bindings.
+	 */
+	legacy_binding = dt_find_property(dev->of_node, "mmu-masters", NULL);
+	if (legacy_binding && !using_generic_binding) {
+		if (!using_legacy_binding)
+			pr_notice("deprecated \"mmu-masters\" DT property in use\n");
+		using_legacy_binding = true;
+	} else if (!legacy_binding && !using_legacy_binding) {
+		using_generic_binding = true;
+	} else {
+		dev_err(dev, "not probing due to mismatched DT properties\n");
+		return -ENODEV;
+	}
 
 	smmu = devm_kzalloc(dev, sizeof(*smmu), GFP_KERNEL);
 	if (!smmu) {
-- 
2.7.4


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