#
# Copyright 2020 NXP
#
# SPDX-License-Identifier:      GPL-2.0+
#

Specifying extra IOMMU mappings for PCI controllers

This feature can be enabled through the PCI_IOMMU_EXTRA_MAPPINGS Kconfig option.

The "pci_iommu_extra" env var or "pci-iommu-extra" device tree property (to be
used for example in more static scenarios such as hardwired PCI endpoints that
get initialized later in the system setup) allows two things:
 - for a SRIOV capable PCI EP identified by its B.D.F specify the maximum number
   of VFs that will ever be created for it
 - for hot-plug case, specify the B.D.F with which the device will show up on
   the PCI bus

The env var consists of a list of <bdf>,<action> pairs for a certain pci bus
identified by its controller's base register address, as defined in the "reg"
property in the device tree.

pci_iommu_extra = pci@<addr1>,<bdf>,<action>,<bdf>,<action>,
                  pci@<addr2>,<bdf>,<action>,<bdf>,<action>,...

where:
 <addr> is the base register address of the pci controller for which the
        subsequent <bdf>,<action> pairs apply
 <bdf> identifies to which B.D.F the action applies to
 <action> can be:
    - "vfs=<number>" to specify that for the PCI EP identified previously by
      the <bdf> to include mappings for <number> of VFs.
      The variant "noari_vfs=<number>" is available to disable taking ARI into
      account.
    - "hp" to specify that on this <bdf> there will be a hot-plugged device so
      it needs a mapping
The device tree property must be placed under the correct pci controller node
and only the bdf and action pairs need to be specified, like this:

pci-iommu-extra = "<bdf>,<action>,<bdf>,<action>,...";

Note: the env var has priority over the device tree property.

For example, given this configuration on bus 6:

=> pci 6
Scanning PCI devices on bus 6
BusDevFun  VendorId   DeviceId   Device Class       Sub-Class
_____________________________________________________________
06.00.00   0x8086     0x1572     Network controller      0x00
06.00.01   0x8086     0x1572     Network controller      0x00

The following u-boot env var will create iommu mappings for 3 VFs for each PF:

=> setenv pci_iommu_extra pci@0x3800000,6.0.0,vfs=3,6.0.1,vfs=3

For the device tree case, this would be specified like this:

pci-iommu-extra = "6.0.0,vfs=3,6.0.1,vfs=3";

To add an iommu mapping for a hot-plugged device, please see following example:

=> setenv pci_iommu_extra pci@0x3800000,2.16.0,hp

For the device tree case, this would be specified like this:

pci-iommu-extra = "2.16.0,hp";