On Mon, Mar 25, 2024 at 08:44:24AM -0500, Rob Herring wrote: > On Mon, Mar 25, 2024 at 4:28 AM Cristian Marussi > <cristian.marussi@xxxxxxx> wrote: > > > > Add bindings for the ARM MHUv3 Mailbox controller. > > Hi Rob, thanks for having a look. > > Signed-off-by: Cristian Marussi <cristian.marussi@xxxxxxx> > > --- > > .../bindings/mailbox/arm,mhuv3.yaml | 239 ++++++++++++++++++ > > 1 file changed, 239 insertions(+) > > create mode 100644 Documentation/devicetree/bindings/mailbox/arm,mhuv3.yaml > > > > diff --git a/Documentation/devicetree/bindings/mailbox/arm,mhuv3.yaml b/Documentation/devicetree/bindings/mailbox/arm,mhuv3.yaml > > new file mode 100644 > > index 000000000000..bfb8ec341d26 > > --- /dev/null > > +++ b/Documentation/devicetree/bindings/mailbox/arm,mhuv3.yaml > > @@ -0,0 +1,239 @@ > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > > +%YAML 1.2 > > +--- > > +$id: http://devicetree.org/schemas/mailbox/arm,mhuv3.yaml# > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > + > > +title: ARM MHUv3 Mailbox Controller > > + > > +maintainers: > > + - Sudeep Holla <sudeep.holla@xxxxxxx> > > + - Cristian Marussi <cristian.marussi@xxxxxxx> > > + > > +description: | > > + The Arm Message Handling Unit (MHU) Version 3 is a mailbox controller that > > + enables unidirectional communications with remote processors through various > > + possible transport protocols. > > + The controller can optionally support a varying number of extensions that, in > > + turn, enable different kinds of transport to be used for communication. > > + Number, type and characteristics of each supported extension can be discovered > > + dynamically at runtime. > > + > > + Given the unidirectional nature of the controller, an MHUv3 mailbox controller > > + is composed of a MHU Sender (MHUS) containing a PostBox (PBX) block and a MHU > > + Receiver (MHUR) containing a MailBox (MBX) block, where > > + > > + PBX is used to > > + - Configure the MHU > > + - Send Transfers to the Receiver > > + - Optionally receive acknowledgment of a Transfer from the Receiver > > + > > + MBX is used to > > + - Configure the MHU > > + - Receive Transfers from the Sender > > + - Optionally acknowledge Transfers sent by the Sender > > + > > + Both PBX and MBX need to be present and defined in the DT description if you > > + need to establish a bidirectional communication, since you will have to > > + acquire two distinct unidirectional channels, one for each block. > > + > > + As a consequence both blocks needs to be represented separately and specified > > + as distinct DT nodes in order to properly describe their resources. > > + > > + Note that, though, thanks to the runtime discoverability, there is no need to > > + identify the type of blocks with distinct compatibles. > > + > > + Following are the MHUv3 possible extensions. > > + > > + - Doorbell Extension (DBE): DBE defines a type of channel called a Doorbell > > + Channel (DBCH). DBCH enables a single bit Transfer to be sent from the > > + Sender to Receiver. The Transfer indicates that an event has occurred. > > + When DBE is implemented, the number of DBCHs implemented is between 1 and > > + 128, numbered starting from 0 in ascending order. > > + Each DBCH contains 32 individual fields, referred to as flags, each of which > > + can be used independently. It is possible for the Sender to send multiple > > + Transfers at once using a single DBCH, so long as each Transfer uses > > + a different flag in the DBCH. > > + Optionally, data may be transmitted through an out-of-band shared memory > > + region, wherein the MHU Doorbell is used strictly as an interrupt generation > > + mechanism, but this is out of the scope of these bindings. > > + > > + - FastChannel Extension (FCE): FCE defines a type of channel called a Fast > > + Channel (FCH). FCH is intended for lower overhead communication between > > + Sender and Receiver at the expense of determinism. An FCH allows the Sender > > + to update the channel value at any time, regardless of whether the previous > > + value has been seen by the Receiver. When the Receiver reads the channel's > > + content it gets the last value written to the channel. > > + FCH is considered lossy in nature, and means that the Sender has no way of > > + knowing if, or when, the Receiver will act on the Transfer. > > + FCHs are expected to behave as RAM which generates interrupts when writes > > + occur to the locations within the RAM. > > + When FCE is implemented, the number of FCH that an implementation of the MHU > > + can support is between 1-1024, if the Fast Channel word-size is 32-bits, or > > + between 1-512, when the Fast Channel word-size is 64-bits. > > Be consistent: FastChannel > I'll fix. > > + FCHs are numbered from 0 in ascending order. > > + Note that Fast Channel word-size is implementation defined, not configurable > > + but discoverable at run-time. > > + Optionally, data may be transmitted through an out-of-band shared memory > > + region, wherein the MHU FastChannel is used as an interrupt generation > > + mechanism which carries also a pointer to such out-of-band data, but this > > + is out of the scope of these bindings. > > + > > + - FIFO Extension (FE): FE defines a Channel type called a FIFO Channel (FFCH). > > + FFCH allows a Sender to send > > + - Multiple Transfer to the Receiver without having to wait for a previous > > + Transfer to be acknowledged by the Receiver, as long as the FIFO has > > + room for the Transfer. > > + - Transfers which require the Receiver to provide acknowledgment. > > + - Transfers which have in-band payload. > > + In all cases, the data is guaranteed to be observed by the Receiver in the > > + same order which the Sender sent it. > > + When FE is implemented, the number of FFCH an implementation of the MHU can > > + support is between 1 and 64, numbered starting from the 0 in ascending > > + order. The FIFO size is implementation defined and not configurable. > > Size is discoverable or opaque to s/w? > FIFOs depth is the same across all of the implemented FIFO channels (between 1 and 1024 bytes) AND it is actually discoverable at runtime...I forgot to mention that here, I'll fix. > > + Optionally, additional data may be transmitted through an out-of-band shared > > + memory region, wherein the MHU FIFO is used to transmit, in order, a small > > + part of the payload (like a header) and a reference to the shared memory > > + area holding the remaining, bigger, chunk of the payload, but this is out of > > + the scope of these bindings. > > + > > +properties: > > + compatible: > > + const: arm,mhuv3 > > + > > + reg: > > + maxItems: 1 > > + > > + interrupts: > > + minItems: 1 > > + maxItems: 38 > > + > > + interrupt-names: > > + description: | > > + The MHUv3 controller generates a number of events some of which are used > > + to generate interrupts; as a consequence it can expose a varying number of > > + optional PBX/MBX interrupts, representing the events generated during the > > + operation of the various transport protocols associated with different > > + extensions. All interrupts of the MHU are level-sensitive. > > + Some of these optional interrupts are defined per-channel, where the > > + number of channels effectively available is implementation defined and > > + run-time discoverable. > > + In the following, for sake of simplicity, only a limited number of > > + per-channel interrupt names are enumerated, out of all the possible > > + channels allowed by the specification for each extension type. > > + > > + - "combined": PBX/MBX Combined interrupt > > + - "combined-ffch": PBX/MBX FIFO Combined interrupt > > + - "ffch-low-tide-<N>": PBX/MBX FIFO Channel <N> Low Tide interrupt > > + - "ffch-high-tide-<N>": PBX/MBX FIFO Channel <N> High Tide interrupt > > + - "ffch-flush-<N>": PBX/MBX FIFO Channel <N> Flush interrupt > > + - "mbx-dbch-xfer-<N>": MBX Doorbell Channel <N> Transfer interrupt > > + - "mbx-fch-xfer-<N>": MBX Fast Channel <N> Transfer interrupt > > + - "mbx-fchgrp-xfer-<N>": MBX Fast Channel <N> Group Transfer interrupt > > + - "mbx-ffch-xfer-<N>": MBX FIFO Channel <N> Transfer interrupt > > + - "pbx-dbch-xfer-ack-<N>": PBX Doorbell Channel <N> Transfer Ack interrupt > > + - "pbx-ffch-xfer-ack-<N>": PBX FIFO Channel <N> Transfer Ack interrupt > > It would be better to not define these strings twice. You can do > something like this: > > items: > oneOf: > - const: combined > description: ... > - pattern: '^ffch-low-tide-[0-9]+$' > description: ... > > And so on. > Thanks, I'll give it a go. > > + > > + The only mandatory interrupts on the MHU are: > > + - combined > > + - mbx-fch-xfer-<N> but only if mbx-fcgrp-xfer-<N> is not implemented. > > + > > + minItems: 1 > > + maxItems: 38 > > Perhaps a comment on where 38 comes from. AIUI, this is a "should be > enough for now" value. > Yes, I'll add and explanation to justify this. > > + items: > > + enum: > > + - combined > > + - combined-ffch > > + - ffch-low-tide-0 > > + - ffch-low-tide-1 > > + - ffch-low-tide-2 > > + - ffch-low-tide-3 > > + - ffch-high-tide-0 > > + - ffch-high-tide-1 > > + - ffch-high-tide-2 > > + - ffch-high-tide-3 > > + - ffch-flush-0 > > + - ffch-flush-1 > > + - ffch-flush-2 > > + - ffch-flush-3 > > + - mbx-dbch-xfer-0 > > + - mbx-dbch-xfer-1 > > + - mbx-dbch-xfer-2 > > + - mbx-dbch-xfer-3 > > + - mbx-fch-xfer-0 > > + - mbx-fch-xfer-1 > > + - mbx-fch-xfer-2 > > + - mbx-fch-xfer-3 > > + - mbx-fchgrp-xfer-0 > > + - mbx-fchgrp-xfer-1 > > + - mbx-fchgrp-xfer-2 > > + - mbx-fchgrp-xfer-3 > > + - mbx-ffch-xfer-0 > > + - mbx-ffch-xfer-1 > > + - mbx-ffch-xfer-2 > > + - mbx-ffch-xfer-3 > > + - pbx-dbch-xfer-ack-0 > > + - pbx-dbch-xfer-ack-1 > > + - pbx-dbch-xfer-ack-2 > > + - pbx-dbch-xfer-ack-3 > > + - pbx-ffch-xfer-ack-0 > > + - pbx-ffch-xfer-ack-1 > > + - pbx-ffch-xfer-ack-2 > > + - pbx-ffch-xfer-ack-3 > > + > > + '#mbox-cells': > > + description: | > > + The first argument in the consumers 'mboxes' property represents the > > + extension type, the second is for the channel number while the third > > + depends on extension type. > > + > > + Extension type for DBE is 0 and the third parameter represents the > > + doorbell flag number to use. > > + Extension type for FCE is 1, third parameter unused. > > + Extension type for FE is 2, third parameter unused. > > + > > + mboxes = <&mhu 0 0 5>; // DBE, Doorbell Channel Window 0, doorbell flag 5. > > + mboxes = <&mhu 0 1 7>; // DBE, Doorbell Channel Window 1, doorbell flag 7. > > + mboxes = <&mhu 1 0 0>; // FCE, Fast Channel Window 0. > > + mboxes = <&mhu 1 3 0>; // FCE, Fast Channel Window 3. > > + mboxes = <&mhu 2 1 0>; // FE, FIFO Channel Window 1. > > + mboxes = <&mhu 2 7 0>; // FE, FIFO Channel Window 7. > > + const: 3 > > + > > + clocks: > > + maxItems: 1 > > + > > +required: > > + - compatible > > + - reg > > + - interrupts > > + - interrupt-names > > + - '#mbox-cells' > > + > > +additionalProperties: false > > + > > +examples: > > + - | > > + soc { > > + #address-cells = <2>; > > + #size-cells = <2>; > > + > > + mhu_tx: mailbox@2aaa0000 { > > Drop unused labels. > Ok. Thanks, Cristian
