[PATCH v4 01/25] iommu: Add iommu_ops->identity_domain

[Jason Gunthorpe <jgg@xxxxxxxxxx>]

This allows a driver to set a global static to an IDENTITY domain and
the core code will automatically use it whenever an IDENTITY domain
is requested.

By making it always available it means the IDENTITY can be used in error
handling paths to force the iommu driver into a known state. Devices
implementing global static identity domains should avoid failing their
attach_dev ops.

Convert rockchip to use the new mechanism.

Tested-by: Steven Price <steven.price@xxxxxxx>
Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Tested-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
 drivers/iommu/iommu.c          | 3 +++
 drivers/iommu/rockchip-iommu.c | 9 +--------
 include/linux/iommu.h          | 3 +++
 3 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 9e0228ef612b85..bb840a818525ad 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1917,6 +1917,9 @@ static struct iommu_domain *__iommu_domain_alloc(const struct bus_type *bus,
 	if (bus == NULL || bus->iommu_ops == NULL)
 		return NULL;
 
+	if (alloc_type == IOMMU_DOMAIN_IDENTITY && bus->iommu_ops->identity_domain)
+		return bus->iommu_ops->identity_domain;
+
 	domain = bus->iommu_ops->domain_alloc(alloc_type);
 	if (!domain)
 		return NULL;
diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 4054030c323795..4fbede269e6712 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -1017,13 +1017,8 @@ static int rk_iommu_identity_attach(struct iommu_domain *identity_domain,
 	return 0;
 }
 
-static void rk_iommu_identity_free(struct iommu_domain *domain)
-{
-}
-
 static struct iommu_domain_ops rk_identity_ops = {
 	.attach_dev = rk_iommu_identity_attach,
-	.free = rk_iommu_identity_free,
 };
 
 static struct iommu_domain rk_identity_domain = {
@@ -1087,9 +1082,6 @@ static struct iommu_domain *rk_iommu_domain_alloc(unsigned type)
 {
 	struct rk_iommu_domain *rk_domain;
 
-	if (type == IOMMU_DOMAIN_IDENTITY)
-		return &rk_identity_domain;
-
 	if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
 		return NULL;
 
@@ -1214,6 +1206,7 @@ static int rk_iommu_of_xlate(struct device *dev,
 }
 
 static const struct iommu_ops rk_iommu_ops = {
+	.identity_domain = &rk_identity_domain,
 	.domain_alloc = rk_iommu_domain_alloc,
 	.probe_device = rk_iommu_probe_device,
 	.release_device = rk_iommu_release_device,
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index d3164259667599..c3004eac2f88e8 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -254,6 +254,8 @@ struct iommu_iotlb_gather {
  *                    will be blocked by the hardware.
  * @pgsize_bitmap: bitmap of all possible supported page sizes
  * @owner: Driver module providing these ops
+ * @identity_domain: An always available, always attachable identity
+ *                   translation.
  */
 struct iommu_ops {
 	bool (*capable)(struct device *dev, enum iommu_cap);
@@ -287,6 +289,7 @@ struct iommu_ops {
 	const struct iommu_domain_ops *default_domain_ops;
 	unsigned long pgsize_bitmap;
 	struct module *owner;
+	struct iommu_domain *identity_domain;
 };
 
 /**
-- 
2.40.1