> Subject: Re: [PATCH V2 1/2] DT: mailbox: add binding doc for the ARM SMC > mailbox > > On Mon, 3 Jun 2019 17:56:51 +0100 > Sudeep Holla <sudeep.holla@xxxxxxx> wrote: > > Hi, > > > On Mon, Jun 03, 2019 at 09:22:16AM -0700, Florian Fainelli wrote: > > > On 6/3/19 1:30 AM, peng.fan@xxxxxxx wrote: > > > > From: Peng Fan <peng.fan@xxxxxxx> > > > > > > > > The ARM SMC mailbox binding describes a firmware interface to > > > > trigger actions in software layers running in the EL2 or EL3 exception > levels. > > > > The term "ARM" here relates to the SMC instruction as part of the > > > > ARM instruction set, not as a standard endorsed by ARM Ltd. > > > > > > > > Signed-off-by: Peng Fan <peng.fan@xxxxxxx> > > > > --- > > > > > > > > V2: > > > > Introduce interrupts as a property. > > > > > > > > V1: > > > > arm,func-ids is still kept as an optional property, because there > > > > is no defined SMC funciton id passed from SCMI. So in my test, I > > > > still use arm,func-ids for ARM SIP service. > > > > > > > > .../devicetree/bindings/mailbox/arm-smc.txt | 101 > +++++++++++++++++++++ > > > > 1 file changed, 101 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 000000000000..401887118c09 > > > > --- /dev/null > > > > +++ b/Documentation/devicetree/bindings/mailbox/arm-smc.txt > > > > @@ -0,0 +1,101 @@ > > > > [...] > > > > > > +Optional properties: > > > > +- arm,func-ids An array of 32-bit values specifying the function > > > > + 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. > > > > +- interrupts SPI interrupts may be listed for notification, > > > > + each channel should use a dedicated interrupt > > > > + line. > > > > > > I would not go about defining a specific kind of interrupt, since > > > SPI is a GIC terminology, this firmware interface could be used in > > > premise with any parent interrupt controller, for which the concept > > > of a SPI/PPI/SGI may not be relevant. > > > > > > > While I agree the binding document may not contain specifics, I still > > don't see how to use SGI with this. Also note it's generally reserved > > for OS future use(IPC) and using this for other than IPC may be bit > > challenging IMO. It opens up lots of questions. > > Well, a PPI might be possible to use, although it's somewhat dodgy to hijack > the GIC's (re-)distributor from EL3 to write to GICD_ISPENDR<n>. Need to ask > Marc about his feelings towards this. But it's definitely possible from a > hypervisor to inject arbitrary interrupts into a guest. > > But more importantly: is there any actual reason this needs to be a GIC > interrupt? No. I just test ATF with SPI when I posting out this. Should not restrict to be GIC. If I understand the code correctly, this could just be any interrupt, > including one of an interrupt combiner or a GPIO chip. So why not just use the > standard wording of: "exactly one interrupt specifier for each channel"? Agree. > > By the way: Shouldn't new bindings use the YAML format instead? I'll convert to YAML in next version. Thanks, Peng. > > Cheers, > Andre.
