On Fri, Jan 23, 2015 at 4:44 AM, Viresh Kumar viresh.kumar@linaro.org wrote:
Rob et al,
This is another attempt to redefine OPP bindings which we concluded to after first round of reviews.
Current OPP (Operating performance point) DT bindings are proven to be insufficient at multiple instances.
There had been multiple band-aid approaches to get them fixed (The latest one being: http://www.mail-archive.com/devicetree@vger.kernel.org/msg53398.html). For obvious reasons Rob rejected them and shown the right path forward.
The shortcomings we are trying to solve here:
How to select which driver to probe for a platform, when multiple drivers are available. For example: how to choose between cpufreq-dt and arm_big_little drivers.
Getting clock sharing information between CPUs. Single shared clock vs independent clock per core vs shared clock per cluster.
I'd like to see acks from Qualcomm folks to make sure this works for them.
Support for turbo modes
Support for intermediate frequencies
Other per OPP settings: transition latencies, disabled status, etc.?
Please see the below bindings for further details.
I haven't incorporated the comments given by Mark Brown as I had some doubts. @broonie: Is this what you wanted to mention earlier ? : http://pastebin.com/1RZTccmm
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org
Documentation/devicetree/bindings/power/opp.txt | 309 +++++++++++++++++++++++- 1 file changed, 308 insertions(+), 1 deletion(-)
diff --git a/Documentation/devicetree/bindings/power/opp.txt b/Documentation/devicetree/bindings/power/opp.txt index 74499e5033fc..9cdc0c9b09af 100644 --- a/Documentation/devicetree/bindings/power/opp.txt +++ b/Documentation/devicetree/bindings/power/opp.txt @@ -1,9 +1,316 @@ -* Generic OPP Interface +Generic OPP (Operating Performance Points) Interface +----------------------------------------------------
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.
+This documents defines OPP bindings with its required/optional properties. OPPs +can be defined for any device, this file uses CPU as an example to illustrate +how to define OPPs.
+opp nodes and opp-lists
+- opp-listN:
- List of nodes defining performance points. Following belong to the nodes
- within the opp-lists.
I still don't think we need this extra level. More below on this.
- Required properties:
- opp-khz: Frequency in kHz
- opp-microvolt: voltage in micro Volts
This can be optional as it is valid to have frequency scaling without voltage scaling. More so for bus scaling than cpu scaling.
- Optional properties:
- turbo-mode: Marks the volt-freq pair as turbo pair.
- status: Marks the node enabled/disabled.
- voltage-tolerance: Specify the CPU voltage tolerance in percentage.
- clock-latency-ns: Specify the possible maximum transition latency (in
- nanoseconds) for switching to this opp from any other opp.
+- oppN:
- Operating performance point node per device. Devices using it should have its
- phandle in their "operating-points-v2" property.
- Required properties:
- compatible: allow OPPs to express their compatibility.
- opp-list: phandle to opp-list defined above.
- Optional properties:
- opp-intermediate: Stable opp we *must* switch to, before switching to the
- target opp. Contains phandle of one of the opp-node present in opp-list.
What about cases where perhaps you have a more complex sequencing arrangement? For example, what if you have to hit each step (to go from A -> D you have to go A -> B -> C -> D). Perhaps each OPP could have an opp-next property which lists other OPPs you can transition to (and no property means no restriction).
Do you have a specific user in mind? If not, I think we can defer this issue. I think the binding is flexible enough to accommodate this in the future.
[...]
+Example 2: Quad-core krait (All CPUs have independent clock lines but have same set of OPPs)
+/ {
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";opp-supply = <&cpu_supply0>;operating-points-v2 = <&cpu0_opp>;};cpu@1 {compatible = "qcom,krait";reg = <1>;next-level-cache = <&L2>;clocks = <&clk_controller 1>;clock-names = "cpu";opp-supply = <&cpu_supply1>;operating-points-v2 = <&cpu1_opp>;};cpu@2 {compatible = "qcom,krait";reg = <2>;next-level-cache = <&L2>;clocks = <&clk_controller 2>;clock-names = "cpu";opp-supply = <&cpu_supply2>;operating-points-v2 = <&cpu2_opp>;};cpu@3 {compatible = "qcom,krait";reg = <3>;next-level-cache = <&L2>;clocks = <&clk_controller 3>;clock-names = "cpu";opp-supply = <&cpu_supply3>;operating-points-v2 = <&cpu3_opp>;};};cpu0_opp: opp0 {compatible = "linux,cpu-dvfs";
As I said before, drop the linux part. I'm not sure about cpu-dvfs either. Nothing is specific to cpus and you are necessarily doing voltage scaling. You could want to find all cpu OPPs though. Perhaps: "cpu-operating-point", "operating-point";
It is not documented either.
opp-list = <&cpu0_opplist>;opp-intermediate = <&cpu0_intermediate>;cpu0_opplist: opp-list0 {entry00 {opp-khz = <1000000>;opp-microvolt = <975000>;voltage-tolerance = <2>;clock-latency-ns = <300000>;status = "okay";};cpu0_intermediate: entry01 {opp-khz = <1100000>;opp-microvolt = <1000000>;voltage-tolerance = <2>;clock-latency-ns = <300000>;status = "okay";};entry02 {opp-khz = <1200000>;opp-microvolt = <1025000>;voltage-tolerance = <2>;clock-latency-ns = <300000>;status = "okay";turbo-mode;};};};cpu1_opp: opp1 {compatible = "linux,cpu-dvfs";opp-list = <&cpu0_opplist>;opp-intermediate = <&cpu0_intermediate>;};
This doesn't add anything other than some indirection to imply independent OPPs. The only way I know the clocks are not shared is you told me so in the example. I'd still prefer to determine from the clock api whether 2 clocks can be changed independently. That didn't seem to be agreed on, so you could simply add a "shared-opp" property to opp0 to mark an OPP as shared or not. Then you can remove the opp-list and these other cpuX_opp nodes.
Rob