[RFC,3/7] mfd: devicetree: bindings: Add Qualcomm SMD based RPM DT binding

Add binding documentation for the Qualcomm Resource Power Manager (RPM)
using shared memory (Qualcomm SMD) as transport mechanism. This is found
in 8974 and newer based devices.

The binding currently describes the rpm itself and the regulator
subnodes.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
---

Note that this patch extends the rpm dt-bindings header from [1].

[1] https://lkml.org/lkml/2014/9/22/733

 .../devicetree/bindings/mfd/qcom-rpm-smd.txt       |  122 ++++++++++++++++++++
 include/dt-bindings/mfd/qcom-rpm.h                 |   36 ++++++
 2 files changed, 158 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt

On Sep 29, 2014, at 7:34 PM, Bjorn Andersson <Bjorn.Andersson@sonymobile.com> wrote:

> Add binding documentation for the Qualcomm Resource Power Manager (RPM)
> using shared memory (Qualcomm SMD) as transport mechanism. This is found
> in 8974 and newer based devices.
> 
> The binding currently describes the rpm itself and the regulator
> subnodes.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
> ---
> 
> Note that this patch extends the rpm dt-bindings header from [1].
> 
> [1] https://lkml.org/lkml/2014/9/22/733
> 
> .../devicetree/bindings/mfd/qcom-rpm-smd.txt       |  122 ++++++++++++++++++++
> include/dt-bindings/mfd/qcom-rpm.h                 |   36 ++++++
> 2 files changed, 158 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
> 
> diff --git a/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
> new file mode 100644
> index 0000000..a846101
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
> @@ -0,0 +1,122 @@
> +Qualcomm Resource Power Manager (RPM) over SMD
> +
> +This driver is used to interface with the Resource Power Manager (RPM) found in
> +various Qualcomm platforms. The RPM allows each component in the system to vote
> +for state of the system resources, such as clocks, regulators and bus
> +frequencies.
> +
> +- compatible:
> +	Usage: required
> +	Value type: <string>
> +	Definition: must be one of:
> +		    "qcom,rpm-msm8974”

Why not “qcom,rpm-smd”.  I’d like to get Jeff H’s input on how what we do here for compat and distinguish the A-family RPM support vs B-family/RPM-SMD support.

> +
> +- qcom,smd-channels:
> +	Usage: required
> +	Value type: <stringlist>
> +	Definition: Shared Memory Channel used for communication with the RPM
> +

This needs more details.

> +- #address-cells:
> +	Usage: required
> +	Value type: <u32>
> +	Definition: must be 1
> +
> +- #size-cells:
> +	Usage: required
> +	Value type: <u32>
> +	Definition: must be 0
> +
> += SUBDEVICES

As I mentioned for the the RPM binding on a-family, we should split out the devices into their own binding specs.

> +
> +The RPM exposes resources to its subnodes. The below bindings specify the set
> +of valid subnodes that can operate on these resources.
> +
> +== Switch-mode Power Supply regulator
> +
> +- compatible:
> +	Usage: required
> +	Value type: <string>
> +	Definition: must be one of:
> +		    "qcom,rpm-pm8841-smps"
> +		    "qcom,rpm-pm8941-smps"
> +
> +
> +- reg:
> +	Usage: required
> +	Value type: <u32>
> +	Definition: resource as defined in <dt-bindings/mfd/qcom-rpm.h>
> +		    must be one of:
> +		    QCOM_RPM_PM8841_SMPS1 - QCOM_RPM_PM8841_SMPS4,
> +		    QCOM_RPM_PM8941_SMPS1 - QCOM_RPM_PM8941_SMPS3
> +
> +Standard regulator bindings are used inside switch mode power supply subnodes.
> +Check Documentation/devicetree/bindings/regulator/regulator.txt for more
> +details.
> +
> +== Low-dropout regulator
> +
> +- compatible:
> +	Usage: required
> +	Value type: <string>
> +	Definition: must be one of:
> +		    "qcom,rpm-pm8941-ldo"
> +
> +- reg:
> +	Usage: required
> +	Value type: <u32>
> +	Definition: resource as defined in <dt-bindings/mfd/qcom-rpm.h>
> +		    must be one of:
> +		    QCOM_RPM_PM8941_LDO1 - QCOM_RPM_PM8941_LDO24
> +
> +Standard regulator bindings are used inside switch low-dropout regulator
> +subnodes.  Check Documentation/devicetree/bindings/regulator/regulator.txt for
> +more details.
> +
> +== Switch
> +
> +- compatible:
> +	Usage: required
> +	Value type: <string>
> +	Definition: must be one of:
> +		    "qcom,rpm-pm8941-switch"
> +
> +- reg:
> +	Usage: required
> +	Value type: <u32>
> +	Definition: resource as defined in <dt-bindings/mfd/qcom/qcom-rpm.h>
> +		    must be one of:
> +		    QCOM_RPM_PM8941_LVS1 - QCOM_RPM_PM8941_LVS3,
> +		    QCOM_RPM_PM8941_MVS1 - QCOM_RPM_PM8941_MVS2
> +
> +Standard regulator bindings are used inside switch regulator subnodes.  Check
> +Documentation/devicetree/bindings/regulator/regulator.txt for more details.
> +
> += EXAMPLE
> +
> +	#include <dt-bindings/mfd/qcom-rpm.h>
> +
> +	rpm@108000 {
> +		compatible = "qcom,rpm-msm8960";
> +		qcom,smd-channels = "rpm_requests";
> +
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +
> +		pm8941_s1: regulator-s1 {
> +			compatible = "qcom,rpm-pm8941-smps";
> +			reg = <QCOM_RPM_PM8941_SMPS1>;
> +
> +			regulator-min-microvolt = <1300000>;
> +			regulator-max-microvolt = <1300000>;
> +		};
> +
> +		pm8941_l3: pm8941-l3 {
> +			compatible = "qcom,rpm-pm8941-ldo";
> +			reg = <QCOM_RPM_PM8941_LDO3>;
> +
> +			regulator-min-microvolt = <1200000>;
> +			regulator-max-microvolt = <1200000>;
> +		};
> +
> +	};
> +

- k

On Tue 30 Sep 06:46 PDT 2014, Kumar Gala wrote:

> 
> On Sep 29, 2014, at 7:34 PM, Bjorn Andersson <Bjorn.Andersson@sonymobile.com> wrote:
> 
> > diff --git a/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
> > new file mode 100644
> > index 0000000..a846101
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
> > @@ -0,0 +1,122 @@
> > +Qualcomm Resource Power Manager (RPM) over SMD
> > +
> > +This driver is used to interface with the Resource Power Manager (RPM) found in
> > +various Qualcomm platforms. The RPM allows each component in the system to vote
> > +for state of the system resources, such as clocks, regulators and bus
> > +frequencies.
> > +
> > +- compatible:
> > +	Usage: required
> > +	Value type: <string>
> > +	Definition: must be one of:
> > +		    "qcom,rpm-msm8974”
> 
> Why not “qcom,rpm-smd”.  I’d like to get Jeff H’s input on how
> what we do here for compat and distinguish the A-family RPM support vs
> B-family/RPM-SMD support.
> 

I don't see anything indicating changes in the actual communication, but as
this also encodes what resources are exposed we have to keep this specific.

I'm not sure what you mean with distinguish the A and B family, they are
completely different and there are no overlap in compatibles or implementation.

The overlap is in how children are communicating with the rpm, but this is an
implementation detail - and noted in that patch as a future improvement.


I forgot to add Jeff, but did send him a separate email asking for his input on
all this.

> > +
> > +- qcom,smd-channels:
> > +	Usage: required
> > +	Value type: <stringlist>
> > +	Definition: Shared Memory Channel used for communication with the RPM
> > +
> 
> This needs more details.
> 

Not sure what more to add here. It should contain the name of the channel used
for communication with the rpm. For all current platforms this would be
"rpm_requests".

> > +- #address-cells:
> > +	Usage: required
> > +	Value type: <u32>
> > +	Definition: must be 1
> > +
> > +- #size-cells:
> > +	Usage: required
> > +	Value type: <u32>
> > +	Definition: must be 0
> > +
> > += SUBDEVICES
> 
> As I mentioned for the the RPM binding on a-family, we should split out the
> devices into their own binding specs.
> 

Please actually read https://lkml.org/lkml/2014/3/10/567, it's now the third
time I send you that link. If you don't like it then ask Rob to revise his
statement.

For me it makes sense to consolidate the RPM binding in one document rather
than spreading it out in 10 different documents with some implicit
dependencies.

Regards,
Bjorn
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On 9/30/2014 8:37 AM, Bjorn Andersson wrote:
> On Tue 30 Sep 06:46 PDT 2014, Kumar Gala wrote:
>
>>
>> On Sep 29, 2014, at 7:34 PM, Bjorn Andersson <Bjorn.Andersson@sonymobile.com> wrote:
>>
>>> diff --git a/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
>>> new file mode 100644
>>> index 0000000..a846101
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
>>> @@ -0,0 +1,122 @@
>>> +Qualcomm Resource Power Manager (RPM) over SMD
>>> +
>>> +This driver is used to interface with the Resource Power Manager (RPM) found in
>>> +various Qualcomm platforms. The RPM allows each component in the system to vote
>>> +for state of the system resources, such as clocks, regulators and bus
>>> +frequencies.
>>> +
>>> +- compatible:
>>> +	Usage: required
>>> +	Value type: <string>
>>> +	Definition: must be one of:
>>> +		    "qcom,rpm-msm8974”
>>
>> Why not “qcom,rpm-smd”.  I’d like to get Jeff H’s input on how
>> what we do here for compat and distinguish the A-family RPM support vs
>> B-family/RPM-SMD support.
>>
>
> I don't see anything indicating changes in the actual communication, but as
> this also encodes what resources are exposed we have to keep this specific.
>
> I'm not sure what you mean with distinguish the A and B family, they are
> completely different and there are no overlap in compatibles or implementation.
>
> The overlap is in how children are communicating with the rpm, but this is an
> implementation detail - and noted in that patch as a future improvement.
>
>
> I forgot to add Jeff, but did send him a separate email asking for his input on
> all this.
>

Yep.  I saw the series.  Still doing a deep dive.

The rpm-smd driver (and the A family equivalent) is outside of my area 
of expertise, but I have some familiarity with it as it is a SMD client. 
  Internally we have a singular compat for all of B family, but I 
haven't been able to figure out how that works to expose all of the 
resources.  I'll talk to my contact later in the week to see what the 
differences are.

Is the per target compat the way to do this though?  The way its 
currently done means we'll have atleast a dozen tables in 
qcom-smd-rpm.c, and I can't imagine they will have anything more than 
minor differences from the msm8x74_resource_table that currently exists 
in patch 6 of the series.  Why wouldn't one table that is a superset of 
all supported targets work?

>>> +
>>> +- qcom,smd-channels:
>>> +	Usage: required
>>> +	Value type: <stringlist>
>>> +	Definition: Shared Memory Channel used for communication with the RPM
>>> +
>>
>> This needs more details.
>>
>
> Not sure what more to add here. It should contain the name of the channel used
> for communication with the rpm. For all current platforms this would be
> "rpm_requests".
>
>>> +- #address-cells:
>>> +	Usage: required
>>> +	Value type: <u32>
>>> +	Definition: must be 1
>>> +
>>> +- #size-cells:
>>> +	Usage: required
>>> +	Value type: <u32>
>>> +	Definition: must be 0
>>> +
>>> += SUBDEVICES
>>
>> As I mentioned for the the RPM binding on a-family, we should split out the
>> devices into their own binding specs.
>>
>
> Please actually read https://lkml.org/lkml/2014/3/10/567, it's now the third
> time I send you that link. If you don't like it then ask Rob to revise his
> statement.
>
> For me it makes sense to consolidate the RPM binding in one document rather
> than spreading it out in 10 different documents with some implicit
> dependencies.
>
> Regards,
> Bjorn
>


Jeffrey Hugo

On Tue 30 Sep 16:16 PDT 2014, Jeffrey Hugo wrote:

> On 9/30/2014 8:37 AM, Bjorn Andersson wrote:
> > On Tue 30 Sep 06:46 PDT 2014, Kumar Gala wrote:
> >
> >>
> >> On Sep 29, 2014, at 7:34 PM, Bjorn Andersson <Bjorn.Andersson@sonymobile.com> wrote:
> >>
> >>> diff --git a/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
> >>> new file mode 100644
> >>> index 0000000..a846101
> >>> --- /dev/null
> >>> +++ b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
> >>> @@ -0,0 +1,122 @@
> >>> +Qualcomm Resource Power Manager (RPM) over SMD
> >>> +
> >>> +This driver is used to interface with the Resource Power Manager (RPM) found in
> >>> +various Qualcomm platforms. The RPM allows each component in the system to vote
> >>> +for state of the system resources, such as clocks, regulators and bus
> >>> +frequencies.
> >>> +
> >>> +- compatible:
> >>> +	Usage: required
> >>> +	Value type: <string>
> >>> +	Definition: must be one of:
> >>> +		    "qcom,rpm-msm8974”
> >>
> >> Why not “qcom,rpm-smd”.  I’d like to get Jeff H’s input on how
> >> what we do here for compat and distinguish the A-family RPM support vs
> >> B-family/RPM-SMD support.
> >>
> >
> > I don't see anything indicating changes in the actual communication, but as
> > this also encodes what resources are exposed we have to keep this specific.
> >
> > I'm not sure what you mean with distinguish the A and B family, they are
> > completely different and there are no overlap in compatibles or implementation.
> >
> > The overlap is in how children are communicating with the rpm, but this is an
> > implementation detail - and noted in that patch as a future improvement.
> >
> >
> > I forgot to add Jeff, but did send him a separate email asking for his input on
> > all this.
> >
> 
> Yep.  I saw the series.  Still doing a deep dive.
> 
> The rpm-smd driver (and the A family equivalent) is outside of my area 
> of expertise, but I have some familiarity with it as it is a SMD client. 
>   Internally we have a singular compat for all of B family, but I 
> haven't been able to figure out how that works to expose all of the 
> resources.  I'll talk to my contact later in the week to see what the 
> differences are.
> 

That's right, because you have these tables in devicetree in the caf version.
You have to have this information somewhere!

> Is the per target compat the way to do this though?  The way its 
> currently done means we'll have atleast a dozen tables in 
> qcom-smd-rpm.c, and I can't imagine they will have anything more than 
> minor differences from the msm8x74_resource_table that currently exists 
> in patch 6 of the series.  Why wouldn't one table that is a superset of 
> all supported targets work?
> 

It would work as long as e.g. QCOM_RPM_PM8941_MVS1 always is vsa number 4.

But sure, it's a much better fit than the family a and this rpm would reject
invalid resources, so it might work. But this works without us knowing about
all possible platforms.


But if the case is that multiple platforms expose the same table we can always
tie the same table to multiple compatibles.

Regards,
Bjorn
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On 9/30/2014 6:08 PM, Bjorn Andersson wrote:
> On Tue 30 Sep 16:16 PDT 2014, Jeffrey Hugo wrote:
>
>> On 9/30/2014 8:37 AM, Bjorn Andersson wrote:
>>> On Tue 30 Sep 06:46 PDT 2014, Kumar Gala wrote:
>>>
>>>>
>>>> On Sep 29, 2014, at 7:34 PM, Bjorn Andersson <Bjorn.Andersson@sonymobile.com> wrote:
>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
>>>>> new file mode 100644
>>>>> index 0000000..a846101
>>>>> --- /dev/null
>>>>> +++ b/Documentation/devicetree/bindings/mfd/qcom-rpm-smd.txt
>>>>> @@ -0,0 +1,122 @@
>>>>> +Qualcomm Resource Power Manager (RPM) over SMD
>>>>> +
>>>>> +This driver is used to interface with the Resource Power Manager (RPM) found in
>>>>> +various Qualcomm platforms. The RPM allows each component in the system to vote
>>>>> +for state of the system resources, such as clocks, regulators and bus
>>>>> +frequencies.
>>>>> +
>>>>> +- compatible:
>>>>> +	Usage: required
>>>>> +	Value type: <string>
>>>>> +	Definition: must be one of:
>>>>> +		    "qcom,rpm-msm8974”
>>>>
>>>> Why not “qcom,rpm-smd”.  I’d like to get Jeff H’s input on how
>>>> what we do here for compat and distinguish the A-family RPM support vs
>>>> B-family/RPM-SMD support.
>>>>
>>>
>>> I don't see anything indicating changes in the actual communication, but as
>>> this also encodes what resources are exposed we have to keep this specific.
>>>
>>> I'm not sure what you mean with distinguish the A and B family, they are
>>> completely different and there are no overlap in compatibles or implementation.
>>>
>>> The overlap is in how children are communicating with the rpm, but this is an
>>> implementation detail - and noted in that patch as a future improvement.
>>>
>>>
>>> I forgot to add Jeff, but did send him a separate email asking for his input on
>>> all this.
>>>
>>
>> Yep.  I saw the series.  Still doing a deep dive.
>>
>> The rpm-smd driver (and the A family equivalent) is outside of my area
>> of expertise, but I have some familiarity with it as it is a SMD client.
>>    Internally we have a singular compat for all of B family, but I
>> haven't been able to figure out how that works to expose all of the
>> resources.  I'll talk to my contact later in the week to see what the
>> differences are.
>>
>
> That's right, because you have these tables in devicetree in the caf version.
> You have to have this information somewhere!

True, it must exist somewhere.  However since its information tied 
directly to the hardware, it seems like its information that would fit 
right in DT.

I talked to my contact, and it seems like the table attributes vary more 
than I thought, target to target, so the single table design seems less 
plausible.  Its my understanding you've had an offline discussion with 
him and some of our regulator guys to discuss the specifics of our 
needs.  I'll let them take over as the experts.

>
>> Is the per target compat the way to do this though?  The way its
>> currently done means we'll have atleast a dozen tables in
>> qcom-smd-rpm.c, and I can't imagine they will have anything more than
>> minor differences from the msm8x74_resource_table that currently exists
>> in patch 6 of the series.  Why wouldn't one table that is a superset of
>> all supported targets work?
>>
>
> It would work as long as e.g. QCOM_RPM_PM8941_MVS1 always is vsa number 4.
>
> But sure, it's a much better fit than the family a and this rpm would reject
> invalid resources, so it might work. But this works without us knowing about
> all possible platforms.
>
>
> But if the case is that multiple platforms expose the same table we can always
> tie the same table to multiple compatibles.
>
> Regards,
> Bjorn
>

On Wed 08 Oct 14:47 PDT 2014, Jeffrey Hugo wrote:

> On 9/30/2014 6:08 PM, Bjorn Andersson wrote:
> > On Tue 30 Sep 16:16 PDT 2014, Jeffrey Hugo wrote:
> >
> >> On 9/30/2014 8:37 AM, Bjorn Andersson wrote:
[..]
> >
> > That's right, because you have these tables in devicetree in the caf version.
> > You have to have this information somewhere!
> 
> True, it must exist somewhere.  However since its information tied 
> directly to the hardware, it seems like its information that would fit 
> right in DT.
> 

For family B it would be reasonable to move this to device tree, replacing my
"reg" property with a "resource" property taking type and id for the resource
(e.g resource = <0x616f646c 17>; for ldo 17).

For family A this does not work thought, but maybe we should just skip the idea
of having a common look in favour of not having the tables.

> I talked to my contact, and it seems like the table attributes vary more 
> than I thought, target to target, so the single table design seems less 
> plausible.  Its my understanding you've had an offline discussion with 
> him and some of our regulator guys to discuss the specifics of our 
> needs.  I'll let them take over as the experts.
> 

Yes, I met with Stephen, David and Mahesh to discuss the matter. The issues
that we discussed was:

1) It must be possible to set the active and sleep state of a resource
independently.

2) Deferring less important writes (e.g. writes to sleep state) to reduce
communication

3) With deferred writes, we need to flush the data when going to sleep and that
requires some special handling - so that we don't wake up again or crash the
rpm.

4) The scalability of the table


I'm working on figuring out how to do 1) in a sane way, as this is needed.

2) gives 3) which gives a bunch of implementation awkwardness and I'm still not
convinced that it is a problem beyond someones KPI, so I will have to do some
measurements. If nothing else it's "just" an optimization that we should be
able to add incrementally later.

I guess 4) is a matter of taste, with the table the client reference a
resource, with all the data in DT it also describes part of how the rpm works.

Regards,
Bjorn
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