On Wed, Oct 7, 2020 at 10:28 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote: > > This patch adds device tree binding for ARM Message Handling Unit (MHU) > controller version 2. > > Based on earlier work by Morten Borup Petersen. > > Co-developed-by: Morten Borup Petersen <morten.petersen@xxxxxxx> > Signed-off-by: Morten Borup Petersen <morten.petersen@xxxxxxx> > Signed-off-by: Tushar Khandelwal <tushar.khandelwal@xxxxxxx> > Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> > > --- > Morten/Tushar, > > I have prepared this based on the best of my understanding about the > hardware, but since I haven't worked on the actual hardware yet there > are chances that I may have misunderstood some of it. Please lemme know > if any of my understanding is incorrect. > > Here is the link to the previous attempt by Tushar to get it upstreamed > long back: > > https://lore.kernel.org/lkml/20190717192616.1731-1-tushar.khandelwal@xxxxxxx/ > > This is very much a new approach and so I am not pointing out the > differences from the previous one. > > I haven't started with redesigning the driver as of now and would like > to get some feedback on the bindings first. Thanks in advance. > --- > .../bindings/mailbox/arm,mhuv2.yaml | 170 ++++++++++++++++++ > 1 file changed, 170 insertions(+) > create mode 100644 Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml > > diff --git a/Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml b/Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml > new file mode 100644 > index 000000000000..3cbdc97f1f4c > --- /dev/null > +++ b/Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml > @@ -0,0 +1,170 @@ > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/mailbox/arm,mhuv2.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: ARM MHUv2 Mailbox Controller > + > +maintainers: > + - Morten Borup Petersen <morten.petersen@xxxxxxx> > + - Viresh Kumar <viresh.kumar@xxxxxxxxxx> > + > +description: | > + The Arm Message Handling Unit (MHU) Version 2 is a mailbox controller that has > + between 1 and 124 channel windows (each 32-bit wide) to provide unidirectional > + communication with remote processor(s), where the number of channel windows > + are implementation dependent. > + > + Given the unidirectional nature of the controller, an MHUv2 mailbox may only > + be written to or read from. If a pair of MHU controllers is implemented > + between two processing elements to provide bidirectional communication, these > + must be specified as two separate mailboxes. > + > + If the interrupts property is present in device tree node, then its treated as > + a receiver mailbox, otherwise a sender. > + > + An MHU controller must be specified along with the supported transport > + protocols. The transport protocols determine the method of data transmission > + as well as the number of provided mailbox channels. > + > + Following are the possible transport protocols. > + > + - Doorbell: Each transfer is made up of single bit flag, using any one of the > + bits in a channel window. A channel window can support up to 32 doorbells > + and the entire window shall be used in doorbell mode. Optionally, data may > + be transmitted through a shared memory region, wherein the MHU is used > + strictly as an interrupt generation mechanism but that is out of the scope > + of these bindings. > + > + - Single-word: Each transfer is single word, using a single Channel window. > + > + - Multi-word: Each transfer is made of two or more words, using two or more > + channel windows. > + > +# We need a select here so we don't match all nodes with 'arm,primecell' > +select: > + properties: > + compatible: > + contains: > + const: arm,mhuv2 > + required: > + - compatible > + > +properties: > + compatible: > + items: > + - const: arm,mhuv2 > + - const: arm,primecell > + > + reg: > + maxItems: 1 > + > + interrupts: > + maxItems: 1 > + > + clocks: > + maxItems: 1 > + > + clock-names: > + items: > + - const: apb_pclk Just 'maxItems: 1' is fine here as the name is already defined. > + > + arm-mhuv2-mode: arm,mhuv2-mode. Needs a type reference. > + description: | > + The MHUv2 controller may contain up to 124 channel windows (each 32-bit > + wide). The hardware and the DT bindings allows any combination of those to > + be used for various transport protocols. > + > + This property allows a platform to describe how these channel windows are > + used in various transport protocols. The entries in this property shall be > + present as an array of tuples, where each tuple describes details about > + one of the transport protocol being implemented over some channel > + window(s). > + > + The first field of a tuple signifies the transfer protocol, 0 is reserved > + for doorbell protocol, 1 is reserved for single-word protocol and 2 is > + reserved for multi-word protocol. Using any other value in the first field > + of a tuple makes it invalid. > + > + The second field of a tuple signifies the number of channel windows where > + the protocol would be used. For doorbell protocol this field signifies the > + number of 32-bit channel windows that implement the doorbell protocol. For > + single-word protocol this field signifies the number of 32-bit channel > + windows that implement separate single-word protocol mailbox channels. For > + multi-word protocol this field signifies the number of channel windows > + used for a multi-word protocol, it should be 2 or more. These are based on IP configuration or a software decision? > + The total number of channel windows specified here shouldn't be more than > + the ones implemented by the platform. But can be less? Then do you need this to be a mask or range? > + > + mhu: mailbox@2b1f0000 { > + ... > + > + arm-mhuv2-mode = <0 2>, <1 3>, <2 5>, <2 7>; > + } > + > + The above example defines the mode of an ARM MHUv2 mailbox controller, > + where a total of 17 channel windows are used. The first two windows are > + used in doorbell mode (64 doorbells), the next 3 windows are (separately) > + used in single-word mode, and the last two mailbox channels are used in > + multi-word mode of length 5 and 7 channel windows. > + > + '#mbox-cells': > + description: | > + It contains two fields, the first field represents the channel number, > + which may be used in doorbell, single-word, or multi-word mode, and the > + second field (only relevant in doorbell mode, ignored otherwise) > + represents the doorbell number within the 32 bit wide channel window. > + > + From the example given above for the arm-mhuv2-mode, here is how a client > + node can reference them. > + > + mboxes = <&mhu 0 5>; // Mailbox channel 0, doorbell 5. > + mboxes = <&mhu 1 7>; // Mailbox channel 1, doorbell 7. > + mboxes = <&mhu 2 0>; // Mailbox channel 2, single-word mode. > + mboxes = <&mhu 4 0>; // Mailbox channel 4, single-word mode. > + mboxes = <&mhu 6 0>; // Mailbox channel 6, multi-word mode with 7 windows. > + > + const: 2 > + > +required: > + - compatible > + - reg > + - '#mbox-cells' > + - arm-mhuv2-mode > + > +additionalProperties: false > + > +examples: > + # Multiple transport protocols implemented by the mailbox controller > + # configured in sender mode > + - | > + soc { > + #address-cells = <2>; > + #size-cells = <2>; > + > + mhu: mailbox@2b1f0000 { > + #mbox-cells = <2>; > + compatible = "arm,mhuv2", "arm,primecell"; > + reg = <0 0x2b1f0000 0 0x1000>; > + clocks = <&clock 0>; > + clock-names = "apb_pclk"; > + arm-mhuv2-mode = <1 5>, <2 2>, <2 5>, <2 7>, <0 2>; > + }; > + > + mhu_client: scb@2e000000 { > + compatible = "fujitsu,mb86s70-scb-1.0"; > + reg = <0 0x2e000000 0 0x4000>; > + > + mboxes = > + //single-word protocol channel 0 > + <&mhu 0 0>, > + //single-word protocol channel 4 > + <&mhu 4 0>, > + //multi-word protocol channel 6 with 5 windows > + <&mhu 6 0>, > + //doorbell protocol channel 9, doorbell 27 > + <&mhu 9 27>; > + }; > + }; > -- > 2.25.0.rc1.19.g042ed3e048af >
