On Tue, Aug 09, 2016 at 12:53:00PM +0100, Andre Przywara wrote: > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx> > --- > .../devicetree/bindings/mailbox/arm-smc.txt | 53 ++++++++++++++++++++++ > 1 file changed, 53 insertions(+) > create mode 100644 Documentation/devicetree/bindings/mailbox/arm-smc.txt > > diff --git a/Documentation/devicetree/bindings/mailbox/arm-smc.txt b/Documentation/devicetree/bindings/mailbox/arm-smc.txt > new file mode 100644 > index 0000000..9919a12 > --- /dev/null > +++ b/Documentation/devicetree/bindings/mailbox/arm-smc.txt > @@ -0,0 +1,53 @@ > +ARM SMC Mailbox Driver > +====================== > + > +This mailbox driver uses the ARM smc (secure monitor call) instruction to > +trigger a mailbox-connected activity in firmware running on the very same > +core as the caller. By nature this operation is synchronous and this > +driver provides no way for asynchronous messages to be delivered the other > +way round, from firmware to the OS. However the value of r0/w0 the firmware > +returns after the smc call is delivered as a received message to the > +mailbox framework, so a synchronous communication can be established. Clever > + > +One usecase of this mailbox is the SCP interface, which uses shared memory > +to transfer commands and parameters and mailboxes to trigger a function > +call. This driver allows SoC without a separate management processor (or > +when such a processor is not available or used) to use this standardized > +interface anyway. > + > +The driver requires no special hardware, any core which supports the SMC > +instruction can be used. This requires firmware in monitor mode/EL3 to > +handle the mailbox message. > + > +Mailbox Device Node: > +==================== > + > +Required properties: > +-------------------- > +- compatible: Shall be "arm,smc-mbox" > +- #mbox-cells Shall be 1 - the index of the channel needed. > +- identifiers An array of 32-bit values specifying the function Minimally, needs 'arm' prefix. 'identifiers' is pretty vague. Perhaps 'arm,smc-func-ids' to say exactly what they are. > + IDs used by each mailbox channel. Those function IDs > + follow the ARM SMC calling convention standard [1]. > + There is one identifier per channel and the number > + of supported channels is determined by the length > + of this array. > + > +Example: > +-------- > + > + mailbox: smc_mbox { > + #mbox-cells = <1>; > + compatible = "arm,smc-mbox"; > + identifiers = <0x82000001 0x82000002>; > + }; > + > + scpi { > + compatible = "arm,scpi"; > + mboxes = <&mailbox 0>; > + shmem = <&cpu_scp_shmem>; > + }; > + > + > +[1] > +http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0028a/index.html > -- > 2.9.0 > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html