Message-ID: <4e64838c-b727-923b-b6d5-413a0681977c@baylibre.com>
Date:   Fri, 17 Feb 2023 13:10:38 +0100
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Subject: Re: [PATCH v1 1/4] dt-bindings: mfd: Add DT bindings for TI TPS6594
 PMIC
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        lee@kernel.org, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, corbet@lwn.net
Cc:     hdegoede@redhat.com, eric.auger@redhat.com, jgg@ziepe.ca,
        razor@blackwall.org, suma.hegde@amd.com,
        stephen@networkplumber.org, arnd@arndb.de,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, eblanc@baylibre.com,
        jneanne@baylibre.com
References: <20230216114410.183489-1-jpanis@baylibre.com>
 <20230216114410.183489-2-jpanis@baylibre.com>
 <c50503f0-dce1-a3b0-2973-8a22b5ef8bc2@linaro.org>
Content-Language: en-US
From:   Julien Panis <jpanis@baylibre.com>
In-Reply-To: <c50503f0-dce1-a3b0-2973-8a22b5ef8bc2@linaro.org>
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On 2/17/23 10:06, Krzysztof Kozlowski wrote:
> On 16/02/2023 12:44, Julien Panis wrote:
>> TPS6594 is a Power Management IC which provides regulators and others
> Subject: drop second/last, redundant "DT bindings for". The
> "dt-bindings" prefix is already stating that these are bindings.
>
>
>> features like GPIOs, RTC, watchdog, ESMs (Error Signal Monitor), and
>> PFSM (Pre-configurable Finite State Machine) managing the state of the
>> device.
>> TPS6594 is the super-set device while TPS6593 and LP8764X are derivatives.
>>
>> Signed-off-by: Julien Panis <jpanis@baylibre.com>
>> ---
>>   .../devicetree/bindings/mfd/ti,tps6594.yaml   | 164 ++++++++++++++++++
>>   1 file changed, 164 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/mfd/ti,tps6594.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/mfd/ti,tps6594.yaml b/Documentation/devicetree/bindings/mfd/ti,tps6594.yaml
>> new file mode 100644
>> index 000000000000..37968d6c0420
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/mfd/ti,tps6594.yaml
>> @@ -0,0 +1,164 @@
>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/mfd/ti,tps6594.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: TI TPS6594 Power Management Integrated Circuit
>> +
>> +maintainers:
>> +  - Julien Panis <jpanis@baylibre.com>
>> +
>> +description: |
>> +  TPS6594 is a Power Management IC which provides regulators and others
>> +  features like GPIOs, RTC, watchdog, ESMs (Error Signal Monitor), and
>> +  PFSM (Pre-configurable Finite State Machine) managing the state of the device.
>> +  TPS6594 is the super-set device while TPS6593 and LP8764X are derivatives.
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - ti,tps6594
>> +      - ti,tps6593
>> +      - ti,lp8764x
> Any particular choice of ordering (different than alphabetical)?

Thank you for the review.

I chose this ordering because it emphasizes the fact that tps6593 and 
lp8764x
are derivatives of tps6594 : tps6593 is nearly the same (a minor feature 
is not
supported), and lp8764x has less resources (less bucks/LDO, and no RTC).

Besides, a multi-PMIC synchronization scheme is implemented in the PMIC 
device
to synchronize the power state changes with other PMIC devices. This is done
through a SPMI bus : the master PMIC is the controller device on the 
SPMI bus,
and the slave PMICs are the target devices on the SPMI bus. For the 5 boards
we work on (for which device trees will be sent in another patch series):
- tps6594 is used on 3 boards and is always master (multi-PMIC config)
- tps6593 is used on 1 board and is master (single-PMIC config)
- lp8764x is used on 2 boards and is always slave (multi-PMIC config)
There might not be situations in which lp8764x would be master and tps6594
or tps6593 would be slave.

That's why I preferred this ordering.

Do you think that alphabetical order would be better ?

>
>> +
>> +  reg:
>> +    description: I2C slave address or SPI chip select number.
>> +    maxItems: 1
>> +
>> +  ti,use-crc:
>> +    type: boolean
>> +    description: If true, use CRC for I2C and SPI interface protocols.
> Hm, why different boards would like to enable or disable it? Why this
> suits DT?

You're right. Reading your comment, it appears to me that CRC feature is 
not fully
related to HW description and should not be set in DT.

CRC is not 'fully' related to HW, but...
For CRC feature as well, PMICs are synchronized (for boards with 
multi-PMIC config).
To use CRC mode, this feature must be requested explicitly on the master 
PMIC
through I2C or SPI driver, then it is enabled for the slave PMICs 
through SPMI bus: that
sync is performed 'automatically', without intervention from the I2C or 
SPI driver to
enable CRC on slave PMICs.
As a consequence, CRC feature is enabled for all PMICs at I2C/SPI driver 
probe,
or it is let disabled for all PMICs. But it can't be enabled for one 
PMIC and disabled
for another one.

This will probably rediscussed for I2C/SPI drivers, but do you think 
that a 'use_crc'
driver parameter would be an acceptable solution ? If so, the master 
PMIC would have
to be identified, so that the driver can explicitly enable CRC mode for 
this one if
'use_crc' is true. With this solution, some 'ti,is-master;' bool 
property would be necessary.

>
>> +
>> +  system-power-controller: true
>> +
>> +  interrupts:
>> +    maxItems: 1
>> +
>> +  ti,multi-phase-id:
>> +    description: |
>> +      Describes buck multi-phase configuration, if any. For instance, XY id means
>> +      that outputs of buck converters X and Y are combined in multi-phase mode.
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    enum: [12, 34, 123, 1234]
>> +
>> +patternProperties:
>> +  "^buck([1-5]|12|34|123|1234)-supply$":
>> +    description: Input supply phandle for each buck.
>> +
>> +  "^ldo[1-4]-supply$":
>> +    description: Input supply phandle for each ldo.
>> +
>> +  regulators:
> This should go to properties, not patternProperties.
>
>> +    type: object
>> +    description: List of regulators provided by this controller.
>> +
>> +    patternProperties:
>> +      "^buck([1-5]|12|34|123|1234)$":
>> +        type: object
>> +        $ref: /schemas/regulator/regulator.yaml#
>> +
>> +        unevaluatedProperties: false
>> +
>> +      "^ldo[1-4]$":
>> +        type: object
>> +        $ref: /schemas/regulator/regulator.yaml#
>> +
>> +        unevaluatedProperties: false
>> +
> You could add here - on this level - of indentation allOf:if for
> excluding setups
>
> if:
>    required:
>      - buck12
> then:
>    properties:
>      buck123: false
>      buck1234: false
>
> Or, if you want to require regulator then:
> oneOf:
>    - required:
>        - buck12
>    - required:
>        - buck123
>    - required:
>        - buck1234
>
> and anyway exclude buck34 with two above.

I am not sure that we have the same understanding of the multi-phase setup.
Maybe the description I wrote is not clear enough (?) Or I just don't 
understand
what you mean exactly.

How would you combine outputs of bucks 3 and 4 ?
We use 'buck34' property to mean that:
  - buck1 output is mono-phase,
  - buck2 output is mono-phase,
  - buck3 and buck4 outputs are combined (i.e. multi-phases).
This weird configuration is supported by these PMICs.

Using a PMIC without using the provided regulators does not seem very 
interesting
indeed.
But strictly speaking, these regulators are not required. One could use 
some others
resources provided by the PMIC (the Error Signal Monitor device for 
instance).
Besides, multi-phase mode depends on the chosen design and is not 
required for
all situations.

>
>> +    additionalProperties: false
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - interrupts
>> +
>> +additionalProperties: false
>
>
> Best regards,
> Krzysztof
>