[PATCH v6 1/8] Documentation: add DT binding for ARM System Control and Power Interface(SCPI) protocol
Sudeep Holla
sudeep.holla at arm.com
Fri Jul 31 10:43:04 PDT 2015
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 at arm.com>
Acked-by: Mark Rutland <mark.rutland at arm.com>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Rob Herring <robh+dt at kernel.org>
CC: Jassi Brar <jassisinghbrar at gmail.com>
Cc: Liviu Dudau <Liviu.Dudau at arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
Cc: Jon Medhurst (Tixy) <tixy at linaro.org>
Cc: devicetree at vger.kernel.org
---
Documentation/devicetree/bindings/arm/arm,scpi.txt | 150 +++++++++++++++++++++
MAINTAINERS | 6 +
2 files 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..e309249db536
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/arm,scpi.txt
@@ -0,0 +1,150 @@
+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://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 at 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 at 0 {
+ compatible = "arm,juno-scp-shmem";
+ reg = <0x0 0x200>;
+ };
+
+ cpu_scp_hpri: scp-shmem at 200 {
+ compatible = "arm,juno-scp-shmem";
+ reg = <0x200 0x200>;
+ };
+};
+
+mailbox: mailbox0 at 40000000 {
+ ....
+ #mbox-cells = <1>;
+};
+
+scpi_protocol: scpi at 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 at 0 {
+ compatible = "arm,scpi-dvfs-clocks";
+ #clock-cells = <1>;
+ clock-indices = <0>, <1>, <2>;
+ clock-output-names = "atlclk", "aplclk","gpuclk";
+ };
+ scpi_clk: scpi_clocks at 3 {
+ compatible = "arm,scpi-variable-clocks";
+ #clock-cells = <1>;
+ clock-indices = <3>, <4>;
+ clock-output-names = "pxlclk0", "pxlclk1";
+ };
+ };
+};
+
+cpu at 0 {
+ ...
+ reg = <0 0>;
+ clocks = <&scpi_dvfs 0>;
+};
+
+hdlcd at 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 at 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 at 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"
diff --git a/MAINTAINERS b/MAINTAINERS
index 9289ecb57b68..7dadaa87afac 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8960,6 +8960,12 @@ W: http://www.sunplus.com
S: Supported
F: arch/score/
+SYSTEM CONTROL & POWER INTERFACE (SCPI) Message Protocol drivers
+M: Sudeep Holla <sudeep.holla at arm.com>
+L: linux-arm-kernel at lists.infradead.org
+S: Maintained
+F: Documentation/devicetree/bindings/arm/arm,scpi.txt
+
SCSI CDROM DRIVER
M: Jens Axboe <axboe at kernel.dk>
L: linux-scsi at vger.kernel.org
--
1.9.1
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