The number of bus types that the IOMMU subsystem deals with is small and
manageable, so pull that list into core code as a first step towards
cleaning up all the boilerplate bus-awareness from drivers. Calling
iommu_probe_device() before bus->iommu_ops is set will simply return
-ENODEV and not break the notifier call chain, so there should be no
harm in proactively registering all our bus notifiers at init time.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com> # s390
Tested-by: Niklas Schnelle <schnelle@linux.ibm.com> # s390
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v4: Squash iommu_bus_init() entirely, for maximum simplicity. Ignoring
    the return from bus_register_notifier() is common, so hopefully it's
    all pretty self-explanatory now.

 drivers/iommu/iommu.c | 72 ++++++++++++++++++++++---------------------
 1 file changed, 37 insertions(+), 35 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 780fb7071577..a8d14f2a1035 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c

@@ -6,6 +6,7 @@

 #define pr_fmt(fmt)    "iommu: " fmt

+#include <linux/amba/bus.h>
 #include <linux/device.h>
 #include <linux/dma-iommu.h>
 #include <linux/kernel.h>

@@ -16,11 +17,13 @@
 #include <linux/export.h>
 #include <linux/slab.h>
 #include <linux/errno.h>
+#include <linux/host1x_context_bus.h>
 #include <linux/iommu.h>
 #include <linux/idr.h>
 #include <linux/err.h>
 #include <linux/pci.h>
 #include <linux/bitops.h>
+#include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/fsl/mc.h>
 #include <linux/module.h>

@@ -75,6 +78,8 @@ static const char * const iommu_group_resv_type_string[] = {
 #define IOMMU_CMD_LINE_DMA_API         BIT(0)
 #define IOMMU_CMD_LINE_STRICT          BIT(1)

+static int iommu_bus_notifier(struct notifier_block *nb,
+                             unsigned long action, void *data);
 static int iommu_alloc_default_domain(struct iommu_group *group,
                                      struct device *dev);
 static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,

@@ -103,6 +108,22 @@ struct iommu_group_attribute iommu_group_attr_##_name =            \
 static LIST_HEAD(iommu_device_list);
 static DEFINE_SPINLOCK(iommu_device_lock);

+static struct bus_type * const iommu_buses[] = {
+       &platform_bus_type,
+#ifdef CONFIG_PCI
+       &pci_bus_type,
+#endif
+#ifdef CONFIG_ARM_AMBA
+       &amba_bustype,
+#endif
+#ifdef CONFIG_FSL_MC_BUS
+       &fsl_mc_bus_type,
+#endif
+#ifdef CONFIG_TEGRA_HOST1X_CONTEXT_BUS
+       &host1x_context_device_bus_type,
+#endif
+};
+
 /*
  * Use a function instead of an array here because the domain-type is a
  * bit-field, so an array would waste memory.

@@ -126,6 +147,8 @@ static const char *iommu_domain_type_str(unsigned int t)

 static int __init iommu_subsys_init(void)
 {
+       struct notifier_block *nb;
+
        if (!(iommu_cmd_line & IOMMU_CMD_LINE_DMA_API)) {
                if (IS_ENABLED(CONFIG_IOMMU_DEFAULT_PASSTHROUGH))
                        iommu_set_default_passthrough(false);

@@ -152,6 +175,15 @@ static int __init iommu_subsys_init(void)
                        (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
                                "(set via kernel command line)" : "");

+       nb = kcalloc(ARRAY_SIZE(iommu_buses), sizeof(*nb), GFP_KERNEL);
+       if (!nb)
+               return -ENOMEM;
+
+       for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
+               nb[i].notifier_call = iommu_bus_notifier;
+               bus_register_notifier(iommu_buses[i], &nb[i]);
+       }
+

        return 0;
 }
 subsys_initcall(iommu_subsys_init);

@@ -1775,39 +1807,6 @@ int bus_iommu_probe(struct bus_type *bus)
        return ret;
 }

-static int iommu_bus_init(struct bus_type *bus, const struct iommu_ops *ops)
-{
-       struct notifier_block *nb;
-       int err;
-
-       nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL);
-       if (!nb)
-               return -ENOMEM;
-
-       nb->notifier_call = iommu_bus_notifier;
-
-       err = bus_register_notifier(bus, nb);
-       if (err)
-               goto out_free;
-
-       err = bus_iommu_probe(bus);
-       if (err)
-               goto out_err;
-
-
-       return 0;
-
-out_err:
-       /* Clean up */
-       bus_for_each_dev(bus, NULL, NULL, remove_iommu_group);
-       bus_unregister_notifier(bus, nb);
-
-out_free:
-       kfree(nb);
-
-       return err;
-}
-
 /**
  * bus_set_iommu - set iommu-callbacks for the bus
  * @bus: bus.

@@ -1836,9 +1835,12 @@ int bus_set_iommu(struct bus_type *bus, const struct iommu_ops *ops)
        bus->iommu_ops = ops;

        /* Do IOMMU specific setup for this bus-type */
-       err = iommu_bus_init(bus, ops);
-       if (err)
+       err = bus_iommu_probe(bus);
+       if (err) {
+               /* Clean up */
+               bus_for_each_dev(bus, NULL, NULL, remove_iommu_group);
                bus->iommu_ops = NULL;
+       }

        return err;
 }
--

2.36.1.dirty