bus: get IOMMU class

API(rte_bus_get_iommu_class) helps to automatically detect and select
appropriate iova mapping scheme for iommu capable device on that bus.

Algorithm for iova scheme selection for bus:
0. Iterate through bus_list.
1. Collect each bus iova mode value and update into 'mode' var.
2. Mode selection scheme is:
if mode == 0 then iova mode is _pa,
if mode == 1 then iova mode is _pa,
if mode == 2 then iova mode is _va,
if mode == 3 then iova mode ia _pa.

So mode !=2  will be default iova mode (_pa).

Signed-off-by: Santosh Shukla <santosh.shukla@caviumnetworks.com>
Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>
Tested-by: Hemant Agrawal <hemant.agrawal@nxp.com>

lib/librte_eal/bsdapp/eal/rte_eal_version.map

@@ -242,6 +242,7 @@ EXPERIMENTAL {
 DPDK_17.11 {
 	global:
 
+	rte_bus_get_iommu_class;
 	rte_pci_get_iommu_class;
 	rte_pci_match;
 

lib/librte_eal/common/eal_common_bus.c

@@ -222,3 +222,26 @@ rte_bus_find_by_device_name(const char *str)
 		c[0] = '\0';
 	return rte_bus_find(NULL, bus_can_parse, name);
 }
+
+
+/*
+ * Get iommu class of devices on the bus.
+ */
+enum rte_iova_mode
+rte_bus_get_iommu_class(void)
+{
+	int mode = RTE_IOVA_DC;
+	struct rte_bus *bus;
+
+	TAILQ_FOREACH(bus, &rte_bus_list, next) {
+
+		if (bus->get_iommu_class)
+			mode |= bus->get_iommu_class();
+	}
+
+	if (mode != RTE_IOVA_VA) {
+		/* Use default IOVA mode */
+		mode = RTE_IOVA_PA;
+	}
+	return mode;
+}

lib/librte_eal/common/eal_common_pci.c

@@ -564,6 +564,7 @@ struct rte_pci_bus rte_pci_bus = {
 		.plug = pci_plug,
 		.unplug = pci_unplug,
 		.parse = pci_parse,
+		.get_iommu_class = rte_pci_get_iommu_class,
 	},
 	.device_list = TAILQ_HEAD_INITIALIZER(rte_pci_bus.device_list),
 	.driver_list = TAILQ_HEAD_INITIALIZER(rte_pci_bus.driver_list),

lib/librte_eal/common/include/rte_bus.h

@@ -183,6 +183,20 @@ struct rte_bus_conf {
 	enum rte_bus_scan_mode scan_mode; /**< Scan policy. */
 };
 
+
+/**
+ * Get common iommu class of the all the devices on the bus. The bus may
+ * check that those devices are attached to iommu driver.
+ * If no devices are attached to the bus. The bus may return with don't care
+ * (_DC) value.
+ * Otherwise, The bus will return appropriate _pa or _va iova mode.
+ *
+ * @return
+ *      enum rte_iova_mode value.
+ */
+typedef enum rte_iova_mode (*rte_bus_get_iommu_class_t)(void);
+
+
 /**
  * A structure describing a generic bus.
  */
@@ -196,6 +210,7 @@ struct rte_bus {
 	rte_bus_unplug_t unplug;     /**< Remove single device from driver */
 	rte_bus_parse_t parse;       /**< Parse a device name */
 	struct rte_bus_conf conf;    /**< Bus configuration */
+	rte_bus_get_iommu_class_t get_iommu_class; /**< Get iommu class */
 };
 
 /**
@@ -295,6 +310,16 @@ struct rte_bus *rte_bus_find_by_device(const struct rte_device *dev);
  */
 struct rte_bus *rte_bus_find_by_name(const char *busname);
 
+
+/**
+ * Get the common iommu class of devices bound on to buses available in the
+ * system. The default mode is PA.
+ *
+ * @return
+ *     enum rte_iova_mode value.
+ */
+enum rte_iova_mode rte_bus_get_iommu_class(void);
+
 /**
  * Helper for Bus registration.
  * The constructor has higher priority than PMD constructors.

lib/librte_eal/linuxapp/eal/rte_eal_version.map

@@ -247,6 +247,7 @@ EXPERIMENTAL {
 DPDK_17.11 {
 	global:
 
+	rte_bus_get_iommu_class;
 	rte_pci_get_iommu_class;
 	rte_pci_match;