Introducing new parameter called xen,scmi-devid to the device-tree bindings.
This parameter should be set for the device nodes, which has
clocks/power-domains/resets working through SCMI.
Given parameter should set the device_id, needed to set device
permissions in the Firmware.
This property is used by Xen hypervisor, which works as trusted Agent,
to set permissions for the devices, passed-through to the Guest Domains,
which are non-trusted Agents. Trusted Agent will use xen,scmi-devid to
set the Device permissions for the Firmware (See Section 4.2.2.10 [0]
for details).
Agents concept is described in Section 4.2.1 [0].
xen,scmi-devid in Device-tree node example:
usb@e6590000
{
xen,scmi-devid = <19>;
clocks = <&scmi_clock 3>, <&scmi_clock 2>;
resets = <&scmi_reset 10>, <&scmi_reset 9>;
power-domains = <&scmi_power 0>;
};
Given example shows the configuration of the hsusb node, which is using
scmi to contol clocks, resets and power-domains. scmi_devid is set
equals to 19, which should match defined id for usb in the Firmware.
Trusted Agent will use xen,scmi-devid to set the device permissions for
the Agents. Guest OS should not have an access to the permissions
settings, so no code to process xen,scmi-devid was presented in Linux
kernel.
We are currently contributing changes to Xen, which are intended to
mediate SCMI access from Guests to the Firmware. Xen uses xen,scmi-devid to set
the permissions for the devices. See [1] thread for details.
[0] https://developer.arm.com/documentation/den0056/latest
[1] https://xen.markmail.org/message/mmi4fpb4qr6e3kad
Oleksii Moisieiev (2):
dt-bindings: Add vendor prefix for Xen hypervisor
dt-bindings: xen: Add xen,scmi-devid property description for SCMI
.../bindings/firmware/xen,scmi-devid.yaml | 42 +++++++++++++++++++
.../devicetree/bindings/vendor-prefixes.yaml | 2 +
2 files changed, 44 insertions(+)
create mode 100644 Documentation/devicetree/bindings/firmware/xen,scmi-devid.yaml
--
2.27.0
