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Date: Fri, 31 Jul 2015 17:00:27 +0100
From: Mark Rutland <mark.rutland@....com>
To: Sudeep Holla <sudeep.holla@....com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Liviu Dudau <Liviu.Dudau@....com>,
Punit Agrawal <Punit.Agrawal@....com>,
"Jon Medhurst (Tixy)" <tixy@...aro.org>,
Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
Kevin Hilman <khilman@...nel.org>,
Rob Herring <robh+dt@...nel.org>,
Jassi Brar <jassisinghbrar@...il.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 1/8] Documentation: add DT binding for ARM System
Control and Power Interface(SCPI) protocol
Hi,
On Thu, Jul 23, 2015 at 12:10:21PM +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 | 151 +++++++++++++++++++++
> MAINTAINERS | 6 +
> 2 files changed, 157 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..e21cce646561
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/arm,scpi.txt
> @@ -0,0 +1,151 @@
> +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 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.
> +
> +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.
Could you change this to:
#clock-cells: Should be 1. Contains the Clock ID value used by SCPI
commands.
That will make it clear what value should be used when writing a dts
(the raw value commands use, as opposed to some logical abstraction
thereof).
With that:
Acked-by: Mark Rutland <mark.rutland@....com>
Thanks,
Mark.
> +- clock-output-names : shall be the corresponding names of the outputs.
> +- clock-indices: The identifying number for the clocks(i.e.clock_id) in the
> + node. 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 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 = "atlclk", "aplclk","gpuclk";
> + };
> + 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>;
> +};
> +
> +hdlcd@...60000 {
> + ...
> + reg = <0 0x7ff60000 0 0x1000>;
> + clocks = <&scpi_clk 4>;
> +};
> +
> +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 '0' as the clock
> +specifier which points to the first entry in the output clocks of
> +scpi_dvfs i.e. "atlclk".
> +
> +Similarly the second example is hdlcd@...60000 and it has pxlclk1 as input
> +clock. '4' in the clock specifier here points to the second entry
> +in the output clocks of scpi_clocks i.e. "pxlclk1"
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a2264167791a..9351b62dbbd7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8955,6 +8955,12 @@ W: http://www.sunplus.com
> S: Supported
> F: arch/score/
>
> +SYSTEM CONTROL & POWER INTERFACE (SCPI) Message Protocol drivers
> +M: Sudeep Holla <sudeep.holla@....com>
> +L: linux-arm-kernel@...ts.infradead.org
> +S: Maintained
> +F: Documentation/devicetree/bindings/arm/arm,scpi.txt
> +
> SCSI CDROM DRIVER
> M: Jens Axboe <axboe@...nel.dk>
> L: linux-scsi@...r.kernel.org
> --
> 1.9.1
>
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