[V6,1/9] PM / OPP: Introduce "power-domain-opp" property

Message ID 025acedb263eaa6089d354d9630214ada8013990.1493203884.git.viresh.kumar@linaro.org
State New
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Series
  • [V6,1/9] PM / OPP: Introduce "power-domain-opp" property
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Commit Message

Viresh Kumar April 26, 2017, 10:57 a.m.
Power-domains need to express their active states in DT and the devices
within the power-domain need to express their dependency on those active
states. The power-domains can use the OPP tables without any
modifications to the bindings.

Add a new property "power-domain-opp", which will contain phandle to the
OPP node of the parent power domain. This is required for devices which
have dependency on the configured active state of the power domain for
their working.

For some platforms the actual frequency and voltages of the power
domains are managed by the firmware and are so hidden from the high
level operating system. The "opp-hz" property is relaxed a bit to
contain indexes instead of actual frequency values to support such
platforms.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

---
 Documentation/devicetree/bindings/opp/opp.txt | 74 ++++++++++++++++++++++++++-
 1 file changed, 73 insertions(+), 1 deletion(-)

-- 
2.12.0.432.g71c3a4f4ba37

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Comments

Rob Herring April 28, 2017, 8:48 p.m. | #1
On Wed, Apr 26, 2017 at 04:27:05PM +0530, Viresh Kumar wrote:
> Power-domains need to express their active states in DT and the devices

> within the power-domain need to express their dependency on those active

> states. The power-domains can use the OPP tables without any

> modifications to the bindings.

> 

> Add a new property "power-domain-opp", which will contain phandle to the

> OPP node of the parent power domain. This is required for devices which

> have dependency on the configured active state of the power domain for

> their working.

> 

> For some platforms the actual frequency and voltages of the power

> domains are managed by the firmware and are so hidden from the high

> level operating system. The "opp-hz" property is relaxed a bit to

> contain indexes instead of actual frequency values to support such

> platforms.

> 

> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

> ---

>  Documentation/devicetree/bindings/opp/opp.txt | 74 ++++++++++++++++++++++++++-

>  1 file changed, 73 insertions(+), 1 deletion(-)

> 

> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt

> index 63725498bd20..6e30cae2a936 100644

> --- a/Documentation/devicetree/bindings/opp/opp.txt

> +++ b/Documentation/devicetree/bindings/opp/opp.txt

> @@ -77,7 +77,10 @@ This defines voltage-current-frequency combinations along with other related

>  properties.

>  

>  Required properties:

> -- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer.

> +- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer. In some

> +  cases the exact frequency in Hz may be hidden from the OS by the firmware and

> +  this field may contain values that represent the frequency in a firmware

> +  dependent way, for example an index of an array in the firmware.


Not really sure OPP binding makes sense here. What about all the other 
properties. We expose voltage, but not freq?

>  

>  Optional properties:

>  - opp-microvolt: voltage in micro Volts.

> @@ -154,6 +157,13 @@ properties.

>  

>  - status: Marks the node enabled/disabled.

>  

> +- power-domain-opp: Phandle to the OPP node of the parent power-domain. The

> +  parent power-domain should be configured to the OPP whose node is pointed by

> +  the phandle, in order to configure the device for the OPP node that contains

> +  this property. The order in which the device and power domain should be

> +  configured is implementation defined. The OPP table of a device can set this

> +  property only if the device node contains "power-domains" property.

> +


I don't even know what to say on this. The continual evolution of 
OPP bindings continues. This seems like further abuse of DT 
power-domains (being a region in a chip that can be powergated) with 
Linux PM domains.

Rob
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Sudeep Holla May 3, 2017, 11:29 a.m. | #2
On 28/04/17 21:48, Rob Herring wrote:
> On Wed, Apr 26, 2017 at 04:27:05PM +0530, Viresh Kumar wrote:

>> Power-domains need to express their active states in DT and the devices

>> within the power-domain need to express their dependency on those active

>> states. The power-domains can use the OPP tables without any

>> modifications to the bindings.

>>

>> Add a new property "power-domain-opp", which will contain phandle to the

>> OPP node of the parent power domain. This is required for devices which

>> have dependency on the configured active state of the power domain for

>> their working.

>>

>> For some platforms the actual frequency and voltages of the power

>> domains are managed by the firmware and are so hidden from the high

>> level operating system. The "opp-hz" property is relaxed a bit to

>> contain indexes instead of actual frequency values to support such

>> platforms.

>>

>> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

>> ---

>>  Documentation/devicetree/bindings/opp/opp.txt | 74 ++++++++++++++++++++++++++-

>>  1 file changed, 73 insertions(+), 1 deletion(-)

>>

>> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt

>> index 63725498bd20..6e30cae2a936 100644

>> --- a/Documentation/devicetree/bindings/opp/opp.txt

>> +++ b/Documentation/devicetree/bindings/opp/opp.txt

>> @@ -77,7 +77,10 @@ This defines voltage-current-frequency combinations along with other related

>>  properties.

>>  

>>  Required properties:

>> -- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer.

>> +- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer. In some

>> +  cases the exact frequency in Hz may be hidden from the OS by the firmware and

>> +  this field may contain values that represent the frequency in a firmware

>> +  dependent way, for example an index of an array in the firmware.

> 

> Not really sure OPP binding makes sense here. What about all the other 

> properties. We expose voltage, but not freq?

> 


I completely agree with that and I have been pushing this to be
represented as just regulators[0]. Mark B seem to dislike that
idea [1]

-- 
Regards,
Sudeep

[0] http://www.spinics.net/lists/devicetree/msg174725.html
[1] http://www.spinics.net/lists/devicetree/msg175113.html
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Kevin Hilman May 6, 2017, 9:58 a.m. | #3
Rob Herring <robh@kernel.org> writes:

> On Wed, Apr 26, 2017 at 04:27:05PM +0530, Viresh Kumar wrote:

>> Power-domains need to express their active states in DT and the devices

>> within the power-domain need to express their dependency on those active

>> states. The power-domains can use the OPP tables without any

>> modifications to the bindings.

>> 

>> Add a new property "power-domain-opp", which will contain phandle to the

>> OPP node of the parent power domain. This is required for devices which

>> have dependency on the configured active state of the power domain for

>> their working.

>> 

>> For some platforms the actual frequency and voltages of the power

>> domains are managed by the firmware and are so hidden from the high

>> level operating system. The "opp-hz" property is relaxed a bit to

>> contain indexes instead of actual frequency values to support such

>> platforms.

>> 

>> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

>> ---

>>  Documentation/devicetree/bindings/opp/opp.txt | 74 ++++++++++++++++++++++++++-

>>  1 file changed, 73 insertions(+), 1 deletion(-)

>> 

>> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt

>> index 63725498bd20..6e30cae2a936 100644

>> --- a/Documentation/devicetree/bindings/opp/opp.txt

>> +++ b/Documentation/devicetree/bindings/opp/opp.txt

>> @@ -77,7 +77,10 @@ This defines voltage-current-frequency combinations along with other related

>>  properties.

>>  

>>  Required properties:

>> -- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer.

>> +- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer. In some

>> +  cases the exact frequency in Hz may be hidden from the OS by the firmware and

>> +  this field may contain values that represent the frequency in a firmware

>> +  dependent way, for example an index of an array in the firmware.

>

> Not really sure OPP binding makes sense here.


I think OPP makes perfect sense here, because microcontroller firmware
is managaging OPPs in hardware.  We just may not know the exact voltage
and/or frequency (and the firmware/hardware may even be doing AVS for
micro-adjustments.)

> What about all the other properties. We expose voltage, but not freq?


I had the same question.  Seems the same comment about an abstract
"index" is needed for voltage also.

>>  

>>  Optional properties:

>>  - opp-microvolt: voltage in micro Volts.

>> @@ -154,6 +157,13 @@ properties.

>>  

>>  - status: Marks the node enabled/disabled.

>>  

>> +- power-domain-opp: Phandle to the OPP node of the parent power-domain. The

>> +  parent power-domain should be configured to the OPP whose node is pointed by

>> +  the phandle, in order to configure the device for the OPP node that contains

>> +  this property. The order in which the device and power domain should be

>> +  configured is implementation defined. The OPP table of a device can set this

>> +  property only if the device node contains "power-domains" property.

>> +


I do understand the need to map a device OPP to a parent power-domain
OPP, but I really don't like another phandle.

First, just because a device OPP changes does not mean that a
power-domain OPP has to change.  What really needs to be specified is a
minimum requirement, not an exact OPP.  IOW, if a device changes OPP,
the power-domain OPP has to be *at least* an OPP that can guarantee that
level of performance, but could also be a more performant OPP, right?

Also, the parent power-domain driver will have a list of all its
devices, and be able to get OPPs from those devices.

IMO, we should do the first (few) implementations of this feature from
the power-domain driver itself, and not try to figure out how to define
this for everyone in DT until we have a better handle on it (pun
intended) ;)

> I don't even know what to say on this. The continual evolution of 

> OPP bindings continues. This seems like further abuse of DT 

> power-domains (being a region in a chip that can be powergated) with 

> Linux PM domains.


Agreed.

Kevin

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Viresh Kumar May 8, 2017, 7:11 a.m. | #4
I had a long chat with Rajendra offline and clarified few things..

On 08-05-17, 11:06, Rajendra Nayak wrote:
> On 05/08/2017 09:45 AM, Viresh Kumar wrote:

> > On 06-05-17, 11:58, Kevin Hilman wrote:


> >> I had the same question.  Seems the same comment about an abstract

> >> "index" is needed for voltage also.

> > 

> > Why should we do that? Here are the cases that I had in mind while writing this:

> > 

> > - DT only contains the performance-index and nothing else (i.e. voltages aren't

> >   exposed).

> > 

> >   We wouldn't be required to fill the microvolt property as it is optional.

> 

> So the performance-index is specified in opp-hz property?


Yes, but in the OPP table of the power-domain and not the device. The
device can still have its own OPP table with normal freq/voltage
values (for a separate regulator).

> What if the microcontroller firmware maps the performance-index to voltage but

> expects linux to scale the frequency?


As you clarified on the chat, you were talking about the device here.
It isn't a problem as we will have two separate tables here, one for
the device and one for the domain.

-- 
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Sudeep Holla May 8, 2017, 1:47 p.m. | #5
On 06/05/17 10:39, Kevin Hilman wrote:
> Sudeep Holla <sudeep.holla@arm.com> writes:

> 

>> On 28/04/17 21:48, Rob Herring wrote:

>>> On Wed, Apr 26, 2017 at 04:27:05PM +0530, Viresh Kumar wrote:

>>>> Power-domains need to express their active states in DT and the devices

>>>> within the power-domain need to express their dependency on those active

>>>> states. The power-domains can use the OPP tables without any

>>>> modifications to the bindings.

>>>>

>>>> Add a new property "power-domain-opp", which will contain phandle to the

>>>> OPP node of the parent power domain. This is required for devices which

>>>> have dependency on the configured active state of the power domain for

>>>> their working.

>>>>

>>>> For some platforms the actual frequency and voltages of the power

>>>> domains are managed by the firmware and are so hidden from the high

>>>> level operating system. The "opp-hz" property is relaxed a bit to

>>>> contain indexes instead of actual frequency values to support such

>>>> platforms.

>>>>

>>>> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

>>>> ---

>>>>  Documentation/devicetree/bindings/opp/opp.txt | 74 ++++++++++++++++++++++++++-

>>>>  1 file changed, 73 insertions(+), 1 deletion(-)

>>>>

>>>> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt

>>>> index 63725498bd20..6e30cae2a936 100644

>>>> --- a/Documentation/devicetree/bindings/opp/opp.txt

>>>> +++ b/Documentation/devicetree/bindings/opp/opp.txt

>>>> @@ -77,7 +77,10 @@ This defines voltage-current-frequency combinations along with other related

>>>>  properties.

>>>>  

>>>>  Required properties:

>>>> -- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer.

>>>> +- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer. In some

>>>> +  cases the exact frequency in Hz may be hidden from the OS by the firmware and

>>>> +  this field may contain values that represent the frequency in a firmware

>>>> +  dependent way, for example an index of an array in the firmware.

>>>

>>> Not really sure OPP binding makes sense here. What about all the other 

>>> properties. We expose voltage, but not freq?

>>>

>>

>> I completely agree with that and I have been pushing this to be

>> represented as just regulators[0]. Mark B seem to dislike that

>> idea [1]

> 

> And Mark is right, because what's being described is not (simply) a

> voltage regultor.  While it might be "just" voltage on some SoCs (for

> now), it is clearly about performance (a.k.a. OPP) on others.

> 


Agreed. What I was against in this particular case was it was just
voltage for the domain and the devices had their own OPP with clocks
described which looks really weird when both are represented as OPPs.

I am fine with OPP representation in all such cases provide the bindings
are well defined especially if they are hierarchical, what takes
precedence, ...etc.

-- 
Regards,
Sudeep
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Kevin Hilman May 12, 2017, 2:59 p.m. | #6
Viresh Kumar <viresh.kumar@linaro.org> writes:

> On 06-05-17, 11:58, Kevin Hilman wrote:

>> Rob Herring <robh@kernel.org> writes:

>> 

>> > On Wed, Apr 26, 2017 at 04:27:05PM +0530, Viresh Kumar wrote:

>> >> Power-domains need to express their active states in DT and the devices

>> >> within the power-domain need to express their dependency on those active

>> >> states. The power-domains can use the OPP tables without any

>> >> modifications to the bindings.

>> >> 

>> >> Add a new property "power-domain-opp", which will contain phandle to the

>> >> OPP node of the parent power domain. This is required for devices which

>> >> have dependency on the configured active state of the power domain for

>> >> their working.

>> >> 

>> >> For some platforms the actual frequency and voltages of the power

>> >> domains are managed by the firmware and are so hidden from the high

>> >> level operating system. The "opp-hz" property is relaxed a bit to

>> >> contain indexes instead of actual frequency values to support such

>> >> platforms.

>> >> 

>> >> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

>> >> ---

>> >>  Documentation/devicetree/bindings/opp/opp.txt | 74 ++++++++++++++++++++++++++-

>> >>  1 file changed, 73 insertions(+), 1 deletion(-)

>> >> 

>> >> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt

>> >> index 63725498bd20..6e30cae2a936 100644

>> >> --- a/Documentation/devicetree/bindings/opp/opp.txt

>> >> +++ b/Documentation/devicetree/bindings/opp/opp.txt

>> >> @@ -77,7 +77,10 @@ This defines voltage-current-frequency combinations along with other related

>> >>  properties.

>> >>  

>> >>  Required properties:

>> >> -- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer.

>> >> +- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer. In some

>> >> +  cases the exact frequency in Hz may be hidden from the OS by the firmware and

>> >> +  this field may contain values that represent the frequency in a firmware

>> >> +  dependent way, for example an index of an array in the firmware.

>> >

>> > Not really sure OPP binding makes sense here.

>> 

>> I think OPP makes perfect sense here, because microcontroller firmware

>> is managaging OPPs in hardware.  We just may not know the exact voltage

>> and/or frequency (and the firmware/hardware may even be doing AVS for

>> micro-adjustments.)

>

> Yes, AVS is being done for the Qcom SoC as well.

>

>> > What about all the other properties. We expose voltage, but not freq?

>> 

>> I had the same question.  Seems the same comment about an abstract

>> "index" is needed for voltage also.

>

> Why should we do that?


For starters, because the lack of it looks very strange upon first read
(notice that both Rob and I pointed that out), and because you didn't
explain why in the first place, it draws attention.

> Here are the cases that I had in mind while writing this:

>

> - DT only contains the performance-index and nothing else (i.e. voltages aren't

>   exposed).

>

>   We wouldn't be required to fill the microvolt property as it is optional.

>

> - DT contains both performance-index and voltages.

>

>   The microvolts property will contain the actual voltages and opp-hz will

>   contain the index.

>

> I don't see why would we like to put some index value in the microvolts

> property. We are setting the index value in the opp-hz property to avoid adding

> extra fields and making sure opp-hz is still the unique property for the nodes.


What about the case where firmware wants exact frequencies, and
microvolts property is just an index?

The point is, you have a very specific SoC and use-case in mind, but the
goal of a binding change like this is to make something that could be
generically useful.

>> >>  

>> >>  Optional properties:

>> >>  - opp-microvolt: voltage in micro Volts.

>> >> @@ -154,6 +157,13 @@ properties.

>> >>  

>> >>  - status: Marks the node enabled/disabled.

>> >>  

>> >> +- power-domain-opp: Phandle to the OPP node of the parent power-domain. The

>> >> +  parent power-domain should be configured to the OPP whose node is pointed by

>> >> +  the phandle, in order to configure the device for the OPP node that contains

>> >> +  this property. The order in which the device and power domain should be

>> >> +  configured is implementation defined. The OPP table of a device can set this

>> >> +  property only if the device node contains "power-domains" property.

>> >> +

>> 

>> I do understand the need to map a device OPP to a parent power-domain

>> OPP, but I really don't like another phandle.

>> 

>> First, just because a device OPP changes does not mean that a

>> power-domain OPP has to change.  What really needs to be specified is a

>> minimum requirement, not an exact OPP.  IOW, if a device changes OPP,

>> the power-domain OPP has to be *at least* an OPP that can guarantee that

>> level of performance, but could also be a more performant OPP, right?

>

> Right and that's how the code is interpreting it right now. Yes, the description

> above should have been more clear on that though.

>

>> Also, the parent power-domain driver will have a list of all its

>> devices, and be able to get OPPs from those devices.

>> 

>> IMO, we should do the first (few) implementations of this feature from

>> the power-domain driver itself, and not try to figure out how to define

>> this for everyone in DT until we have a better handle on it (pun

>> intended) ;)

>

> Hmm, I am not sure how things are going to work in that case. The opp-hz value

> read from the phandle is passed to the QoS framework in this series, which makes

> sure that we select the highest requested performance point for a particular

> power-domain. The index value is required to be present with the OPP framework

> to make it all work, at least based on the way I have designed it for now.


IMO, this kind of dependency isn't the job of the OPP framework, it's
the job of the power-domain governor.

Kevin
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Patch

diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
index 63725498bd20..6e30cae2a936 100644
--- a/Documentation/devicetree/bindings/opp/opp.txt
+++ b/Documentation/devicetree/bindings/opp/opp.txt
@@ -77,7 +77,10 @@  This defines voltage-current-frequency combinations along with other related
 properties.
 
 Required properties:
-- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer.
+- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer. In some
+  cases the exact frequency in Hz may be hidden from the OS by the firmware and
+  this field may contain values that represent the frequency in a firmware
+  dependent way, for example an index of an array in the firmware.
 
 Optional properties:
 - opp-microvolt: voltage in micro Volts.
@@ -154,6 +157,13 @@  properties.
 
 - status: Marks the node enabled/disabled.
 
+- power-domain-opp: Phandle to the OPP node of the parent power-domain. The
+  parent power-domain should be configured to the OPP whose node is pointed by
+  the phandle, in order to configure the device for the OPP node that contains
+  this property. The order in which the device and power domain should be
+  configured is implementation defined. The OPP table of a device can set this
+  property only if the device node contains "power-domains" property.
+
 Example 1: Single cluster Dual-core ARM cortex A9, switch DVFS states together.
 
 / {
@@ -528,3 +538,65 @@  Example 5: opp-supported-hw
 		};
 	};
 };
+
+Example 7: Power domains with their own OPP tables:
+(example: For 1GHz device require domain state 1 and for 1.1 & 1.2 GHz device require state 2)
+
+/ {
+	domain_opp_table: opp_table0 {
+		compatible = "operating-points-v2";
+
+		/*
+		 * NOTE: Actual frequency is managed by firmware and is hidden
+		 * from HLOS, so we simply use index in the opp-hz field to
+		 * select the OPP.
+		 */
+		domain_opp_1: opp-1 {
+			opp-hz = /bits/ 64 <1>;
+			opp-microvolt = <975000 970000 985000>;
+		};
+		domain_opp_2: opp-2 {
+			opp-hz = /bits/ 64 <2>;
+			opp-microvolt = <1075000 1000000 1085000>;
+		};
+	};
+
+	foo_domain: power-controller@12340000 {
+		compatible = "foo,power-controller";
+		reg = <0x12340000 0x1000>;
+		#power-domain-cells = <0>;
+		operating-points-v2 = <&domain_opp_table>;
+	}
+
+	cpu0_opp_table: opp_table1 {
+		compatible = "operating-points-v2";
+		opp-shared;
+
+		opp-1000000000 {
+			opp-hz = /bits/ 64 <1000000000>;
+			power-domain-opp = <&domain_opp_1>;
+		};
+		opp-1100000000 {
+			opp-hz = /bits/ 64 <1100000000>;
+			power-domain-opp = <&domain_opp_2>;
+		};
+		opp-1200000000 {
+			opp-hz = /bits/ 64 <1200000000>;
+			power-domain-opp = <&domain_opp_2>;
+		};
+	};
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		cpu@0 {
+			compatible = "arm,cortex-a9";
+			reg = <0>;
+			clocks = <&clk_controller 0>;
+			clock-names = "cpu";
+			operating-points-v2 = <&cpu0_opp_table>;
+			power-domains = <&foo_domain>;
+		};
+	};
+};