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Message-ID: <20150722084312.GB14923@e106497-lin.cambridge.arm.com>
Date: Wed, 22 Jul 2015 09:43:12 +0100
From: Liviu Dudau <Liviu.Dudau@....com>
To: Sudeep Holla <sudeep.holla@....com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
"Jon Medhurst (Tixy)" <tixy@...aro.org>,
Arnd Bergmann <arnd@...db.de>,
Kevin Hilman <khilman@...nel.org>,
Olof Johansson <olof@...om.net>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <Mark.Rutland@....com>,
Jassi Brar <jassisinghbrar@...il.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 1/8] Documentation: add DT binding for ARM System
Control and Power Interface(SCPI) protocol
Hi Sudeep,
Minor spelling/phrasing corrections:
On Mon, Jun 08, 2015 at 11:39:55AM +0100, Sudeep Holla wrote:
> This patch adds devicetree binding for System Control and Power
> Interface (SCPI) Message Protocol used between the Application Cores(AP)
> and the System Control Processor(SCP). The MHU peripheral provides a
> mechanism for inter-processor communication between SCP's M3 processor
> and AP.
>
> SCP offers control and management of the core/cluster power states,
> various power domain DVFS including the core/cluster, certain system
> clocks configuration, thermal sensors and many others.
>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> CC: Jassi Brar <jassisinghbrar@...il.com>
> Cc: Liviu Dudau <Liviu.Dudau@....com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Cc: Jon Medhurst (Tixy) <tixy@...aro.org>
> Cc: devicetree@...r.kernel.org
> ---
> Documentation/devicetree/bindings/arm/arm,scpi.txt | 156 +++++++++++++++++++++
> 1 file changed, 156 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/arm/arm,scpi.txt
>
> diff --git a/Documentation/devicetree/bindings/arm/arm,scpi.txt b/Documentation/devicetree/bindings/arm/arm,scpi.txt
> new file mode 100644
> index 000000000000..f5f9684e23b3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/arm,scpi.txt
> @@ -0,0 +1,156 @@
> +System Control and Power Interface (SCPI) Message Protocol
> +----------------------------------------------------------
> +
> +Firmware implementing the SCPI described in ARM document number ARM DUI 0922B
> +("ARM Compute Subsystem SCP: Message Interface Protocols")[0] can be used
> +by Linux to initiate various system control and power operations.
> +
> +Required properties:
> +
> +- compatible : should be "arm,scpi"
> +- mboxes: List of phandle and mailbox channel specifiers
> + All the channels reserved by remote SCP firmware for use by
> + SCPI message protocol should be specified in any order
> +- shmem : List of phandle pointing to the shared memory(SHM) area between the
> + processors using these mailboxes for IPC, one for each mailbox
> + SHM can be any memory reserved for the purpose of this communication
> + between the processors.
> +
> +See Documentation/devicetree/bindings/mailbox/mailbox.txt
> +for more details about the generic mailbox controller and
> +client driver bindings.
> +
> +Clock bindings for the clocks based on SCPI Message Protocol
> +------------------------------------------------------------
> +
> +This binding uses the common clock binding[1].
> +
> +Container Node
> +==============
> +Required properties:
> +- compatible : should be "arm,scpi-clocks"
> + All the clocks provided by SCP firmware via SCPI message
> + protocol much be listed as sub-nodes under this node.
> +
> +Sub-nodes
> +=========
> +Required properties:
> +- compatible : shall include one of the following
> + "arm,scpi-dvfs-clocks" - all the clocks that are variable and index based.
> + These clocks don't provide the full range between the limits
... don't provide an entire range of values between the limits
> + but only discrete points within the range. The firmware
> + provides the mapping for each such operating frequency and the
> + index associated with it. The firmware also manages the
> + voltage scaling appropriately with the clock scaling.
> + "arm,scpi-variable-clocks" - all the clocks that are variable and provide full
> + range within the specified range. The firmware provides the
range of values within a specified range. .....
> + supported range for each clock.
> +
> +Other required properties for all clocks(all from common clock binding):
> +- #clock-cells : should be set to 1 as each of the SCPI clocks have multiple
> + outputs. The clock specifier will be the index to an entry in the list
> + of output clocks.
> +- clock-output-names : shall be the corresponding names of the outputs.
> +- clock-indices: The identifyng number for the clocks(clock_id) in the node as
s/identifyng/identifying/
> + expected by the firmware. It can be non linear and hence provide the
> + mapping of identifiers into the clock-output-names array.
> +
> +SRAM and Shared Memory for SCPI
> +-------------------------------
> +
> +A small area of SRAM is reserved for SCPI communication between application
> +processors and SCP.
> +
> +Required properties:
> +- compatible : should be "arm,juno-sram-ns" for Non-secure SRAM on Juno
> +
> +The rest of the properties should follow the generic mmio-sram discription
s/discription/description/
> +found in ../../misc/sysram.txt
> +
> +Each sub-node represents the reserved area for SCPI.
> +
> +Required sub-node properties:
> +- reg : The base offset and size of the reserved area with the SRAM
> +- compatible : should be "arm,juno-scp-shmem" for Non-secure SRAM based
> + shared memory on Juno platforms
> +
> +[0] http://community.arm.com/servlet/JiveServlet/download/8401-45-18326/DUI0922B_scp_message_interface.pdf
> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
> +
> +Example:
> +
> +sram: sram@...00000 {
> + compatible = "arm,juno-sram-ns", "mmio-sram";
> + reg = <0x0 0x50000000 0x0 0x10000>;
> +
> + #address-cells = <1>;
> + #size-cells = <1>;
> + ranges = <0 0x0 0x50000000 0x10000>;
> +
> + cpu_scp_lpri: scp-shmem@0 {
> + compatible = "arm,juno-scp-shmem";
> + reg = <0x0 0x200>;
> + };
> +
> + cpu_scp_hpri: scp-shmem@200 {
> + compatible = "arm,juno-scp-shmem";
> + reg = <0x200 0x200>;
> + };
> +};
> +
> +mailbox: mailbox0@...00000 {
> + ....
> + #mbox-cells = <1>;
> +};
> +
> +scpi_protocol: scpi@...00000 {
> + compatible = "arm,scpi";
> + mboxes = <&mailbox 0 &mailbox 1>;
> + shmem = <&cpu_scp_lpri &cpu_scp_hpri>;
> +
> + clocks {
> + compatible = "arm,scpi-clocks";
> +
> + scpi_dvfs: scpi_clocks@0 {
> + compatible = "arm,scpi-dvfs-clocks";
> + #clock-cells = <1>;
> + clock-indices = <0>, <1>, <2>;
> + clock-output-names = "vbig", "vlittle", "vgpu";
> + };
> + scpi_clk: scpi_clocks@3 {
> + compatible = "arm,scpi-variable-clocks";
> + #clock-cells = <1>;
> + clock-indices = <3>, <4>;
> + clock-output-names = "pxlclk0", "pxlclk1";
> + };
> + };
> +};
> +
> +cpu@0 {
> + ...
> + reg = <0 0>;
> + clocks = <&scpi_dvfs 0>;
> + clock-names = "vbig";
> +};
> +
> +hdlcd@...60000 {
> + ...
> + reg = <0 0x7ff60000 0 0x1000>;
> + clocks = <&scpi_clk 1>;
> + clock-names = "pxlclk";
> +};
> +
> +In the above example, the #clock-cells is set to 1 as required.
> +scpi_dvfs has 3 output clocks namely: vbig, vlittle and vgpu with 0, 1
> +and 2 as clock-indices. scpi_clk has 2 output clocks namely: pxlclk0 and
> +pxlclk1 with 3 and 4 as clock-indices.
> +
> +The first consumer in the example is cpu@0 and it has vbig as input clock.
> +The index '0' in the clock specifier here points to the first entry in the
> +output clocks of scpi_dvfs for which clock_id asrequired by the firmware
s/asrequired/as required/
> +is 0.
> +
> +Similarly the second example is hdlcd@...60000 and it has pxlclk0 as input
> +clock. The index '1' in the clock specifier here points to the second entry
> +in the output clocks of scpi_clocks for which clock_id as required by the
> +firmware is 4.
This paragraph doesn't match the example. pxlclk0 is index '0'.
Best regards,
Liviu
> --
> 1.9.1
>
--
====================
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
¯\_(ツ)_/¯
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