Re: [PATCH v2 1/8] dt-bindings: pinctrl: mvebu: Document bindings for AC5

[Chris Packham <Chris.Packham@alliedtelesis.co.nz>]

On 16/03/22 21:16, Krzysztof Kozlowski wrote:
> On 15/03/2022 22:12, Chris Packham wrote:
>> (trimmed cc list to the arm, pinctrl and dt people)
>>
>> On 15/03/22 23:46, Krzysztof Kozlowski wrote:
>>> On 14/03/2022 22:31, Chris Packham wrote:
>>>> Add JSON schema for marvell,ac5-pinctrl present on the Marvell 98DX2530
>>>> SoC.
>>>>
>>>> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
>>>> ---
>>>>
>>>> Notes:
>>>>       Changes in v2:
>>>>       - Remove syscon and simple-mfd compatibles
>>>>
>>>>    .../bindings/pinctrl/marvell,ac5-pinctrl.yaml | 70 +++++++++++++++++++
>>>>    1 file changed, 70 insertions(+)
>>>>    create mode 100644 Documentation/devicetree/bindings/pinctrl/marvell,ac5-pinctrl.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/pinctrl/marvell,ac5-pinctrl.yaml b/Documentation/devicetree/bindings/pinctrl/marvell,ac5-pinctrl.yaml
>>>> new file mode 100644
>>>> index 000000000000..65af1d5f5fe0
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/pinctrl/marvell,ac5-pinctrl.yaml
>>>> @@ -0,0 +1,70 @@
>>>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://scanmail.trustwave.com/?c=20988&d=1pyx4kv4KTrTfE5fXNs54mLZmOgk87Uim6CXu-YC1w&u=http%3a%2f%2fdevicetree%2eorg%2fschemas%2fpinctrl%2fmarvell%2cac5-pinctrl%2eyaml%23
>>>> +$schema: http://scanmail.trustwave.com/?c=20988&d=1pyx4kv4KTrTfE5fXNs54mLZmOgk87Uim6TAvbEE2Q&u=http%3a%2f%2fdevicetree%2eorg%2fmeta-schemas%2fcore%2eyaml%23
>>>> +
>>>> +title: Marvell AC5 pin controller
>>>> +
>>>> +maintainers:
>>>> +  - Chris Packham <chris.packham@alliedtelesis.co.nz>
>>>> +
>>>> +description:
>>>> +  Bindings for Marvell's AC5 memory-mapped pin controller.
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    const: marvell,ac5-pinctrl
>>>> +
>>>> +patternProperties:
>>>> +  '-pins$':
>>>> +    type: object
>>>> +    $ref: pinmux-node.yaml#
>>>> +
>>>> +    properties:
>>>> +      marvell,function:
>>>> +        $ref: "/schemas/types.yaml#/definitions/string"
>>>> +        description:
>>>> +          Indicates the function to select.
>>>> +        enum: [ gpio, i2c0, i2c1, nand, sdio, spi0, spi1, uart0, uart1, uart2, uart3 ]
>>>> +
>>>> +      marvell,pins:
>>>> +        $ref: /schemas/types.yaml#/definitions/string-array
>>>> +        description:
>>>> +          Array of MPP pins to be used for the given function.
>>>> +        minItems: 1
>>>> +        items:
>>>> +          enum: [ mpp0, mpp1, mpp2, mpp3, mpp4, mpp5, mpp6, mpp7, mpp8, mpp9,
>>>> +                  mpp10, mpp11, mpp12, mpp13, mpp14, mpp15, mpp16, mpp17, mpp18, mpp19,
>>>> +                  mpp20, mpp21, mpp22, mpp23, mpp24, mpp25, mpp26, mpp27, mpp28, mpp29,
>>>> +                  mpp30, mpp31, mpp32, mpp33, mpp34, mpp35, mpp36, mpp37, mpp38, mpp39,
>>>> +                  mpp40, mpp41, mpp42, mpp43, mpp44, mpp45 ]
>>>> +
>>>> +allOf:
>>>> +  - $ref: "pinctrl.yaml#"
>>>> +
>>>> +required:
>>>> +  - compatible
>>>> +
>>>> +additionalProperties: false
>>>> +
>>>> +examples:
>>>> +  - |
>>>> +    system-controller@80020100 {
>>>> +      compatible = "syscon", "simple-mfd";
>>>> +      reg = <0x80020000 0x20>;
>>> This is unusual. Usually the pinctrl should be a device @80020100, not
>>> child of syscon node. Why do you need it? In v1 you mentioned that
>>> vendor sources do like this, but it's not correct to copy wrong DTS. :)
>> The vendor dts has this
>>
>>           pinctrl0: pinctrl@80020100 {
>>               compatible = "marvell,ac5-pinctrl",
>>                        "syscon", "simple-mfd";
>>               reg = <0 0x80020100 0 0x20>;
>>               i2c_mpps: i2c-mpps {
>>                   marvell,pins = "mpp26", "mpp27";
>>                   marvell,function = "i2c0-opt";
>>               };
>>        };
>>
>> Rob pointed out that "syscon", "simple-mfd" don't belong. I went looking
>> and found marvell,armada-7k-pinctrl which has the pinctrl as a child of
>> a syscon node and what you see in v2 is the result.
>>
>> I probably went a bit too far off the deep end and should have just
>> dropped the "syscon", "simple-mfd" compatibles. I even wrote that
>> version but decided to add some gold plating before I submitted it.
> More or less it is explained in
> Documentation/devicetree/bindings/arm/marvell/cp110-system-controller.txt why
> armada-7k uses it that way. The pinctrl is part of system registers
> which apparently has to be shared with others (on shared SFR range).
>
> It depends on your case, your SFR ranges for pinctrl and other blocks.
>
I can tell you that without a syscon node in the mix somewhere the 
driver will fail to load. And when I switch to 
mvebu_pinctrl_simple_mmio_probe() the driver loads but then kernel 
panics when something tries to use one of the pin functions.

So I think the syscon is needed. I just need to come up with a better 
justification than "because it's needed".

> Best regards,
> Krzysztof