iommu: Remove iommu_present()

The last callsite of iommu_present() is removed by commit <45c690aea8ee>
("drm/tegra: Use iommu_paging_domain_alloc()"). Remove it to avoid dead
code.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20241009051808.29455-1-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: LuBaolu

drivers/iommu/iommu.c

@@ -1840,31 +1840,6 @@ int bus_iommu_probe(const struct bus_type *bus)
 	return 0;
 }
 
-/**
- * iommu_present() - make platform-specific assumptions about an IOMMU
- * @bus: bus to check
- *
- * Do not use this function. You want device_iommu_mapped() instead.
- *
- * Return: true if some IOMMU is present and aware of devices on the given bus;
- * in general it may not be the only IOMMU, and it may not have anything to do
- * with whatever device you are ultimately interested in.
- */
-bool iommu_present(const struct bus_type *bus)
-{
-	bool ret = false;
-
-	for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
-		if (iommu_buses[i] == bus) {
-			spin_lock(&iommu_device_lock);
-			ret = !list_empty(&iommu_device_list);
-			spin_unlock(&iommu_device_lock);
-		}
-	}
-	return ret;
-}
-EXPORT_SYMBOL_GPL(iommu_present);
-
 /**
  * device_iommu_capable() - check for a general IOMMU capability
  * @dev: device to which the capability would be relevant, if available

include/linux/iommu.h

@@ -785,7 +785,6 @@ static inline void iommu_iotlb_gather_init(struct iommu_iotlb_gather *gather)
 }
 
 extern int bus_iommu_probe(const struct bus_type *bus);
-extern bool iommu_present(const struct bus_type *bus);
 extern bool device_iommu_capable(struct device *dev, enum iommu_cap cap);
 extern bool iommu_group_has_isolated_msi(struct iommu_group *group);
 extern struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus);
@@ -1081,11 +1080,6 @@ struct iommu_iotlb_gather {};
 struct iommu_dirty_bitmap {};
 struct iommu_dirty_ops {};
 
-static inline bool iommu_present(const struct bus_type *bus)
-{
-	return false;
-}
-
 static inline bool device_iommu_capable(struct device *dev, enum iommu_cap cap)
 {
 	return false;