Commit 80f390ea authored by Sudeep Holla's avatar Sudeep Holla

Documentation: add DT binding for ARM System Control and Power Interface(SCPI) protocol

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: default avatarSudeep Holla <sudeep.holla@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: Rob Herring <robh+dt@kernel.org>
CC: Jassi Brar <jassisinghbrar@gmail.com>
Cc: Liviu Dudau <Liviu.Dudau@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Jon Medhurst (Tixy) <tixy@linaro.org>
Cc: devicetree@vger.kernel.org
parent 6ff33f39
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 1. Contains the Clock ID value used by SCPI commands.
- 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://infocenter.arm.com/help/topic/com.arm.doc.dui0922b/index.html
[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
Example:
sram: sram@50000000 {
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@40000000 {
....
#mbox-cells = <1>;
};
scpi_protocol: scpi@2e000000 {
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@7ff60000 {
...
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: atlclk, aplclk, and gpuclk 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@7ff60000 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"
...@@ -9149,6 +9149,12 @@ W: http://www.sunplus.com ...@@ -9149,6 +9149,12 @@ W: http://www.sunplus.com
S: Supported S: Supported
F: arch/score/ F: arch/score/
SYSTEM CONTROL & POWER INTERFACE (SCPI) Message Protocol drivers
M: Sudeep Holla <sudeep.holla@arm.com>
L: linux-arm-kernel@lists.infradead.org
S: Maintained
F: Documentation/devicetree/bindings/arm/arm,scpi.txt
SCSI CDROM DRIVER SCSI CDROM DRIVER
M: Jens Axboe <axboe@kernel.dk> M: Jens Axboe <axboe@kernel.dk>
L: linux-scsi@vger.kernel.org L: linux-scsi@vger.kernel.org
......
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