Date: Fri, 11 Aug 2017 15:54:53 +0200
From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
To: Michal Simek <michal.simek@xilinx.com>
CC: Rob Herring <robh@kernel.org>, Edgar Iglesias <edgari@xilinx.com>,
        <linux-arm-kernel@lists.infradead.org>,
        Soren Brinkmann <soren.brinkmann@xilinx.com>,
        <devicetree@vger.kernel.org>, <monstr@monstr.eu>,
        <linux-kernel@vger.kernel.org>, Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH 1/3] dt: xilinx: zynqmp: Add bindings for PM firmware
Message-ID: <20170811135453.GU12347@toto>
References: <cover.1501854302.git.michal.simek@xilinx.com>
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On Fri, Aug 11, 2017 at 02:58:03PM +0200, Michal Simek wrote:
> Hi Rob, +Edgar,
> 
> On 10.8.2017 21:10, Rob Herring wrote:
> > On Fri, Aug 04, 2017 at 03:45:30PM +0200, Michal Simek wrote:
> >> From: Soren Brinkmann <soren.brinkmann@xilinx.com>
> >>
> >> Document the DT bindings for the Zynq UltraScale+ PM Firmware.
> >>
> >> Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
> >> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> >> ---
> >>
> >>  .../devicetree/bindings/soc/xilinx/xlnx,zynqmp-pm.txt | 19 +++++++++++++++++++
> > 
> > bindings/firmware/
> 
> will move.
> 
> > 
> >>  1 file changed, 19 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/soc/xilinx/xlnx,zynqmp-pm.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/soc/xilinx/xlnx,zynqmp-pm.txt b/Documentation/devicetree/bindings/soc/xilinx/xlnx,zynqmp-pm.txt
> >> new file mode 100644
> >> index 000000000000..222a18ce07fc
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/soc/xilinx/xlnx,zynqmp-pm.txt
> >> @@ -0,0 +1,19 @@
> >> +Xilinx Zynq MPSoC Firmware Device Tree Bindings
> >> +
> >> +The zynqmp-pm node describes the interface to platform firmware.
> > 
> > Please define this should be under /firmware node.
> > 
> >> +Required properties:
> >> + - compatible:	Must contain:  "xlnx,zynqmp-pm"
> >> + - method:	The method of calling the PM-API firmware layer.
> >> +		Permitted values are:
> >> +		 - "smc" : To be used in configurations without a hypervisor
> >> +		 - "hvc" : To be used when hypervisor is present
> > 
> > Do you really use both?
> > 
> 
> SMCs definitely yes.
> 
> Interface was designed in that way and I don't know if people are using
> it or not.
> 
> Not sure if Xen is blocking SMCs. I know we have discussed it but not
> sure if this is enabled by default or only for certain configurations.
> Also not sure if xen contains handler for hvc.
> Edgar: Do you know?

We have patches for Xen that implement a power-management mediator.
That implementation handles PM calls over both SMC and HVC insns.
Patches are on the Xen mailing list.

Other hypervisors may work differently.

I think we should support both but I don't have a strong opinion on it.

Cheers,
Edgar