Hi Sudeep,

-----Original Message-----
From: Sudeep Holla [mailto:sudeep.holla@arm.com]
Sent: Thursday, March 01, 2018 6:15 AM
To: Jolly Shah <redacted>; gregkh@linuxfoundation.org;
matt@codeblueprint.co.uk; hkallweit1@gmail.com; michal.simek@xilinx.com;
robh+dt@kernel.org; mark.rutland@arm.com
Cc: ard.biesheuvel@linaro.org; mingo@kernel.org; keescook@chromium.org;
dmitry.torokhov@gmail.com; Sudeep Holla [off-list ref]; Rajan
Vaja [off-list ref]; linux-arm-kernel@lists.infradead.org; linux-
kernel@vger.kernel.org; devicetree@vger.kernel.org; Jolly Shah
[off-list ref]
Subject: Re: [PATCH v5 1/4] dt-bindings: firmware: Add bindings for ZynqMP
firmware



On 20/02/18 19:21, Jolly Shah wrote:

quoted

Add documentation to describe Xilinx ZynqMP firmware driver bindings.
Firmware driver provides an interface to firmware APIs. Interface APIs
can be used by any driver to communicate to PMUFW (Platform Management
Unit).

Signed-off-by: Jolly Shah <redacted>
Signed-off-by: Rajan Vaja <redacted>
---
 .../firmware/xilinx/xlnx,zynqmp-firmware.txt       | 24

++++++++++++++++++++++

quoted

 1 file changed, 24 insertions(+)
 create mode 100644
Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-firmware
.txt

diff --git
a/Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-firmwa
re.txt
b/Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-firmwa
re.txt
new file mode 100644
index 0000000..99434ba

--- /dev/null
+++ b/Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-fi
+++ rmware.txt

@@ -0,0 +1,24 @@
+Xilinx Zynq MPSoC Firmware Device Tree Bindings
+
+The zynqmp-firmware node describes the interface to platform firmware.
+ZynqMP has an interface to communicate with secure firmware. Firmware
+driver provides an interface to firmware APIs. Interface APIs can be
+used by any driver to communicate to PMUFW(Platform Management Unit).
+These requests include clock management, pin control, device control,
+power management service, FPGA service and other platform management
+services.
+
+Required properties:
+ - compatible:	Must contain:  "xlnx,zynqmp-firmware"
+ - method:	The method of calling the PM-API firmware layer.
+		Permitted values are:
+		  - "smc" : SMC #0, following the SMCCC
+		  - "hvc" : HVC #0, following the SMCCC
+
+Examples:
+	firmware {
+		zynqmp_firmware: zynqmp-firmware {
+			compatible = "xlnx,zynqmp-firmware";
+			method = "smc";
+		};
+	};

Do you foresee using SMC/HVC for this firmware even on future platforms?
If not, I suggest to keep the protocol part separate from the transport i.e.
smc/hvc via ATF. It could be replaced with mailbox or some h/w mechanism in
future ?

We have PSCI and EEMI interfaces exposed to linux from ATF.  PSCI is an EEMI client. We do not have current plans to switch to mailbox as it will require 2 communication channels to PMU as PSCI is through ATF. 

--
Regards,
Sudeep