Re: [PATCH 1/2] dt-bindings: power: reset: document the QEMU RISC-V virt machine poweroff device

[Rob Herring <robh@kernel.org>]

On Thu, Nov 07, 2019 at 02:32:01PM -0800, Paul Walmsley wrote:
> On Thu, 7 Nov 2019, Christoph Hellwig wrote:
> 
> > Add the binding for the trivial Qemu RISC-V poweroff mechanism, which is
>
> There's nothing RISC-V specific here.  This IP isn't defined in the RISC-V 
> specifications, or anything like that.  

Does the VM have a spec or anything? Would be nice if it did. Would be 
nicer still to just copy Arm's virt machine.

> Apparently it's a SiFive IP block which now has a virtual IP 
> implementation in QEMU in hw/riscv/sifive_test.c.  But since there's 
> nothing RISC-V specific about this IP block, any QEMU system, with any CPU 
> implementation, should be able to use this virtual IP, and this Linux 
> driver.
> 
> For these reasons, it's better if "RISC-V" is just removed from everywhere 
> in this driver.  If something needs to go in its place, "SiFive" may be 
> better.

IIRC, there's already syscon poweroff binding. You could probably use 
that.

> 
> 
> - Paul
> 
> 
> > just a single MMIO register exposed through the DT.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> >  .../power/reset/qemu-riscv-virt-poweroff.txt     | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/power/reset/qemu-riscv-virt-poweroff.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/power/reset/qemu-riscv-virt-poweroff.txt b/Documentation/devicetree/bindings/power/reset/qemu-riscv-virt-poweroff.txt
> > new file mode 100644
> > index 000000000000..80ff6fd4e3b7
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/power/reset/qemu-riscv-virt-poweroff.txt
> > @@ -0,0 +1,16 @@
> > +QEMU RISC-V virt machine poweroff device
> > +
> > +This is a device in Qemu that can signal successful or error exit
> > +by writing two magic numbers to a trivial mmio register.
> > +A Linux poweroff is implemented as successful exit.
> > +
> > +Required Properties:
> > +-compatible: "sifive,test0"
> > +-reg: Specifies the physical address of the register
> > +
> > +Example:
> > +
> > +	test@100000 {
> > +		compatible = "sifive,test0";
> > +		reg = <0x100000 0x1000>;
> > +	};
> > -- 
> > 2.20.1
> > 
> > 
> 
> 
> - Paul