Skip to content

Commit

Permalink
PM / OPP: Add new bindings to address shortcomings of existing bindings
Browse files Browse the repository at this point in the history 
Current OPP (Operating performance point) device tree bindings have been
insufficient due to the inflexible nature of the original bindings. Over
time, we have realized that Operating Performance Point definitions and
usage is varied depending on the SoC and a "single size (just frequency,
voltage) fits all" model which the original bindings attempted and
failed.

The proposed next generation of the bindings addresses by providing a
expandable binding for OPPs and introduces the following common
shortcomings seen with the original bindings:

- Getting clock/voltage/current rails sharing information between CPUs.
  Shared by all cores vs independent clock per core vs shared clock per
  cluster.

- Support for specifying current levels along with voltages.

- Support for multiple regulators.

- Support for turbo modes.

- Other per OPP settings: transition latencies, disabled status, etc.?

- Expandability of OPPs in future.

This patch introduces new bindings "operating-points-v2" to get these problems
solved. Refer to the bindings for more details.

We now have multiple versions of OPP binding and only one of them should
be used per device.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
  • Loading branch information
Viresh Kumar authored and Rafael J. Wysocki committed Jun 22, 2015
1 parent 0f57d86 commit b901b51
Showing 1 changed file with 377 additions and 4 deletions.
381 changes: 377 additions & 4 deletions Documentation/devicetree/bindings/power/opp.txt
View file
Original file line number Diff line number Diff line change
@@ -1,8 +1,19 @@
* Generic OPP Interface
Generic OPP (Operating Performance Points) Bindings
----------------------------------------------------

SoCs have a standard set of tuples consisting of frequency and
voltage pairs that the device will support per voltage domain. These
are called Operating Performance Points or OPPs.
Devices work at voltage-current-frequency combinations and some implementations
have the liberty of choosing these. These combinations are called Operating
Performance Points aka OPPs. This document defines bindings for these OPPs
applicable across wide range of devices. For illustration purpose, this document
uses CPU as a device.

This document contain multiple versions of OPP binding and only one of them
should be used per device.

Binding 1: operating-points
============================

This binding only supports voltage-frequency pairs.

Properties:
- operating-points: An array of 2-tuples items, and each item consists
Expand All @@ -23,3 +34,365 @@ cpu@0 {
198000 850000
>;
};


Binding 2: operating-points-v2
============================

* Property: operating-points-v2

Devices supporting OPPs must set their "operating-points-v2" property with
phandle to a OPP table in their DT node. The OPP core will use this phandle to
find the operating points for the device.

If required, this can be extended for SoC vendor specfic bindings. Such bindings
should be documented as Documentation/devicetree/bindings/power/<vendor>-opp.txt
and should have a compatible description like: "operating-points-v2-<vendor>".

* OPP Table Node

This describes the OPPs belonging to a device. This node can have following
properties:

Required properties:
- compatible: Allow OPPs to express their compatibility. It should be:
"operating-points-v2".

- OPP nodes: One or more OPP nodes describing voltage-current-frequency
combinations. Their name isn't significant but their phandle can be used to
reference an OPP.

Optional properties:
- opp-shared: Indicates that device nodes using this OPP Table Node's phandle
switch their DVFS state together, i.e. they share clock/voltage/current lines.
Missing property means devices have independent clock/voltage/current lines,
but they share OPP tables.


* OPP Node

This defines voltage-current-frequency combinations along with other related
properties.

Required properties:
- opp-hz: Frequency in Hz

Optional properties:
- opp-microvolt: voltage in micro Volts.

A single regulator's voltage is specified with an array of size one or three.
Single entry is for target voltage and three entries are for <target min max>
voltages.

Entries for multiple regulators must be present in the same order as
regulators are specified in device's DT node.

- opp-microamp: The maximum current drawn by the device in microamperes
considering system specific parameters (such as transients, process, aging,
maximum operating temperature range etc.) as necessary. This may be used to
set the most efficient regulator operating mode.

Should only be set if opp-microvolt is set for the OPP.

Entries for multiple regulators must be present in the same order as
regulators are specified in device's DT node. If this property isn't required
for few regulators, then this should be marked as zero for them. If it isn't
required for any regulator, then this property need not be present.

- clock-latency-ns: Specifies the maximum possible transition latency (in
nanoseconds) for switching to this OPP from any other OPP.

- turbo-mode: Marks the OPP to be used only for turbo modes. Turbo mode is
available on some platforms, where the device can run over its operating
frequency for a short duration of time limited by the device's power, current
and thermal limits.

- status: Marks the node enabled/disabled.

Example 1: Single cluster Dual-core ARM cortex A9, switch DVFS states together.

/ {
cpus {
#address-cells = <1>;
#size-cells = <0>;

cpu@0 {
compatible = "arm,cortex-a9";
reg = <0>;
next-level-cache = <&L2>;
clocks = <&clk_controller 0>;
clock-names = "cpu";
cpu-supply = <&cpu_supply0>;
operating-points-v2 = <&cpu0_opp_table>;
};

cpu@1 {
compatible = "arm,cortex-a9";
reg = <1>;
next-level-cache = <&L2>;
clocks = <&clk_controller 0>;
clock-names = "cpu";
cpu-supply = <&cpu_supply0>;
operating-points-v2 = <&cpu0_opp_table>;
};
};

cpu0_opp_table: opp_table0 {
compatible = "operating-points-v2";
opp-shared;

opp00 {
opp-hz = <1000000000>;
opp-microvolt = <970000 975000 985000>;
opp-microamp = <70000>;
clock-latency-ns = <300000>;
};
opp01 {
opp-hz = <1100000000>;
opp-microvolt = <980000 1000000 1010000>;
opp-microamp = <80000>;
clock-latency-ns = <310000>;
};
opp02 {
opp-hz = <1200000000>;
opp-microvolt = <1025000>;
clock-latency-ns = <290000>;
turbo-mode;
};
};
};

Example 2: Single cluster, Quad-core Qualcom-krait, switches DVFS states
independently.

/ {
cpus {
#address-cells = <1>;
#size-cells = <0>;

cpu@0 {
compatible = "qcom,krait";
reg = <0>;
next-level-cache = <&L2>;
clocks = <&clk_controller 0>;
clock-names = "cpu";
cpu-supply = <&cpu_supply0>;
operating-points-v2 = <&cpu_opp_table>;
};

cpu@1 {
compatible = "qcom,krait";
reg = <1>;
next-level-cache = <&L2>;
clocks = <&clk_controller 1>;
clock-names = "cpu";
cpu-supply = <&cpu_supply1>;
operating-points-v2 = <&cpu_opp_table>;
};

cpu@2 {
compatible = "qcom,krait";
reg = <2>;
next-level-cache = <&L2>;
clocks = <&clk_controller 2>;
clock-names = "cpu";
cpu-supply = <&cpu_supply2>;
operating-points-v2 = <&cpu_opp_table>;
};

cpu@3 {
compatible = "qcom,krait";
reg = <3>;
next-level-cache = <&L2>;
clocks = <&clk_controller 3>;
clock-names = "cpu";
cpu-supply = <&cpu_supply3>;
operating-points-v2 = <&cpu_opp_table>;
};
};

cpu_opp_table: opp_table {
compatible = "operating-points-v2";

/*
* Missing opp-shared property means CPUs switch DVFS states
* independently.
*/

opp00 {
opp-hz = <1000000000>;
opp-microvolt = <970000 975000 985000>;
opp-microamp = <70000>;
clock-latency-ns = <300000>;
};
opp01 {
opp-hz = <1100000000>;
opp-microvolt = <980000 1000000 1010000>;
opp-microamp = <80000>;
clock-latency-ns = <310000>;
};
opp02 {
opp-hz = <1200000000>;
opp-microvolt = <1025000>;
opp-microamp = <90000;
lock-latency-ns = <290000>;
turbo-mode;
};
};
};

Example 3: Dual-cluster, Dual-core per cluster. CPUs within a cluster switch
DVFS state together.

/ {
cpus {
#address-cells = <1>;
#size-cells = <0>;

cpu@0 {
compatible = "arm,cortex-a7";
reg = <0>;
next-level-cache = <&L2>;
clocks = <&clk_controller 0>;
clock-names = "cpu";
cpu-supply = <&cpu_supply0>;
operating-points-v2 = <&cluster0_opp>;
};

cpu@1 {
compatible = "arm,cortex-a7";
reg = <1>;
next-level-cache = <&L2>;
clocks = <&clk_controller 0>;
clock-names = "cpu";
cpu-supply = <&cpu_supply0>;
operating-points-v2 = <&cluster0_opp>;
};

cpu@100 {
compatible = "arm,cortex-a15";
reg = <100>;
next-level-cache = <&L2>;
clocks = <&clk_controller 1>;
clock-names = "cpu";
cpu-supply = <&cpu_supply1>;
operating-points-v2 = <&cluster1_opp>;
};

cpu@101 {
compatible = "arm,cortex-a15";
reg = <101>;
next-level-cache = <&L2>;
clocks = <&clk_controller 1>;
clock-names = "cpu";
cpu-supply = <&cpu_supply1>;
operating-points-v2 = <&cluster1_opp>;
};
};

cluster0_opp: opp_table0 {
compatible = "operating-points-v2";
opp-shared;

opp00 {
opp-hz = <1000000000>;
opp-microvolt = <970000 975000 985000>;
opp-microamp = <70000>;
clock-latency-ns = <300000>;
};
opp01 {
opp-hz = <1100000000>;
opp-microvolt = <980000 1000000 1010000>;
opp-microamp = <80000>;
clock-latency-ns = <310000>;
};
opp02 {
opp-hz = <1200000000>;
opp-microvolt = <1025000>;
opp-microamp = <90000>;
clock-latency-ns = <290000>;
turbo-mode;
};
};

cluster1_opp: opp_table1 {
compatible = "operating-points-v2";
opp-shared;

opp10 {
opp-hz = <1300000000>;
opp-microvolt = <1045000 1050000 1055000>;
opp-microamp = <95000>;
clock-latency-ns = <400000>;
};
opp11 {
opp-hz = <1400000000>;
opp-microvolt = <1075000>;
opp-microamp = <100000>;
clock-latency-ns = <400000>;
};
opp12 {
opp-hz = <1500000000>;
opp-microvolt = <1010000 1100000 1110000>;
opp-microamp = <95000>;
clock-latency-ns = <400000>;
turbo-mode;
};
};
};

Example 4: Handling multiple regulators

/ {
cpus {
cpu@0 {
compatible = "arm,cortex-a7";
...

cpu-supply = <&cpu_supply0>, <&cpu_supply1>, <&cpu_supply2>;
operating-points-v2 = <&cpu0_opp_table>;
};
};

cpu0_opp_table: opp_table0 {
compatible = "operating-points-v2";
opp-shared;

opp00 {
opp-hz = <1000000000>;
opp-microvolt = <970000>, /* Supply 0 */
<960000>, /* Supply 1 */
<960000>; /* Supply 2 */
opp-microamp = <70000>, /* Supply 0 */
<70000>, /* Supply 1 */
<70000>; /* Supply 2 */
clock-latency-ns = <300000>;
};

/* OR */

opp00 {
opp-hz = <1000000000>;
opp-microvolt = <970000 975000 985000>, /* Supply 0 */
<960000 965000 975000>, /* Supply 1 */
<960000 965000 975000>; /* Supply 2 */
opp-microamp = <70000>, /* Supply 0 */
<70000>, /* Supply 1 */
<70000>; /* Supply 2 */
clock-latency-ns = <300000>;
};

/* OR */

opp00 {
opp-hz = <1000000000>;
opp-microvolt = <970000 975000 985000>, /* Supply 0 */
<960000 965000 975000>, /* Supply 1 */
<960000 965000 975000>; /* Supply 2 */
opp-microamp = <70000>, /* Supply 0 */
<0>, /* Supply 1 doesn't need this */
<70000>; /* Supply 2 */
clock-latency-ns = <300000>;
};
};
};

0 comments on commit b901b51

Please sign in to comment.