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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/devicetree/bindings/interrupt-controller/msi.txt | |
parent | Initial commit. (diff) | |
download | linux-430c2fc249ea5c0536abd21c23382884005c9093.tar.xz linux-430c2fc249ea5c0536abd21c23382884005c9093.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/devicetree/bindings/interrupt-controller/msi.txt')
-rw-r--r-- | Documentation/devicetree/bindings/interrupt-controller/msi.txt | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/interrupt-controller/msi.txt b/Documentation/devicetree/bindings/interrupt-controller/msi.txt new file mode 100644 index 000000000..c20b51df7 --- /dev/null +++ b/Documentation/devicetree/bindings/interrupt-controller/msi.txt @@ -0,0 +1,135 @@ +This document describes the generic device tree binding for MSI controllers and +their master(s). + +Message Signaled Interrupts (MSIs) are a class of interrupts generated by a +write to an MMIO address. + +MSIs were originally specified by PCI (and are used with PCIe), but may also be +used with other busses, and hence a mechanism is required to relate devices on +those busses to the MSI controllers which they are capable of using, +potentially including additional information. + +MSIs are distinguished by some combination of: + +- The doorbell (the MMIO address written to). + + Devices may be configured by software to write to arbitrary doorbells which + they can address. An MSI controller may feature a number of doorbells. + +- The payload (the value written to the doorbell). + + Devices may be configured to write an arbitrary payload chosen by software. + MSI controllers may have restrictions on permitted payloads. + +- Sideband information accompanying the write. + + Typically this is neither configurable nor probeable, and depends on the path + taken through the memory system (i.e. it is a property of the combination of + MSI controller and device rather than a property of either in isolation). + + +MSI controllers: +================ + +An MSI controller signals interrupts to a CPU when a write is made to an MMIO +address by some master. An MSI controller may feature a number of doorbells. + +Required properties: +-------------------- + +- msi-controller: Identifies the node as an MSI controller. + +Optional properties: +-------------------- + +- #msi-cells: The number of cells in an msi-specifier, required if not zero. + + Typically this will encode information related to sideband data, and will + not encode doorbells or payloads as these can be configured dynamically. + + The meaning of the msi-specifier is defined by the device tree binding of + the specific MSI controller. + + +MSI clients +=========== + +MSI clients are devices which generate MSIs. For each MSI they wish to +generate, the doorbell and payload may be configured, though sideband +information may not be configurable. + +Required properties: +-------------------- + +- msi-parent: A list of phandle + msi-specifier pairs, one for each MSI + controller which the device is capable of using. + + This property is unordered, and MSIs may be allocated from any combination of + MSI controllers listed in the msi-parent property. + + If a device has restrictions on the allocation of MSIs, these restrictions + must be described with additional properties. + + When #msi-cells is non-zero, busses with an msi-parent will require + additional properties to describe the relationship between devices on the bus + and the set of MSIs they can potentially generate. + + +Example +======= + +/ { + #address-cells = <1>; + #size-cells = <1>; + + msi_a: msi-controller@a { + reg = <0xa 0xf00>; + compatible = "vendor-a,some-controller"; + msi-controller; + /* No sideband data, so #msi-cells omitted */ + }; + + msi_b: msi-controller@b { + reg = <0xb 0xf00>; + compatible = "vendor-b,another-controller"; + msi-controller; + /* Each device has some unique ID */ + #msi-cells = <1>; + }; + + msi_c: msi-controller@c { + reg = <0xc 0xf00>; + compatible = "vendor-b,another-controller"; + msi-controller; + /* Each device has some unique ID */ + #msi-cells = <1>; + }; + + dev@0 { + reg = <0x0 0xf00>; + compatible = "vendor-c,some-device"; + + /* Can only generate MSIs to msi_a */ + msi-parent = <&msi_a>; + }; + + dev@1 { + reg = <0x1 0xf00>; + compatible = "vendor-c,some-device"; + + /* + * Can generate MSIs to either A or B. + */ + msi-parent = <&msi_a>, <&msi_b 0x17>; + }; + + dev@2 { + reg = <0x2 0xf00>; + compatible = "vendor-c,some-device"; + /* + * Has different IDs at each MSI controller. + * Can generate MSIs to all of the MSI controllers. + */ + msi-parent = <&msi_a>, <&msi_b 0x17>, <&msi_c 0x53>; + }; +}; |