linux-kernel - Re: [PATCH v2 1/2] dt-bindings: pinctrl: Add MediaTek MT6795 pinctrl bindings

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Date:   Tue, 3 May 2022 20:33:40 -0400
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     linus.walleij@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, matthias.bgg@...il.com,
        sean.wang@...nel.org, linux-gpio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH v2 1/2] dt-bindings: pinctrl: Add MediaTek MT6795 pinctrl
 bindings

Hi Angelo,

On Tue, May 03, 2022 at 04:25:36PM +0200, AngeloGioacchino Del Regno wrote:
> Add devicetree and pinfunc bindings for MediaTek Helio X10 MT6795.
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
>  .../pinctrl/mediatek,pinctrl-mt6795.yaml      | 224 +++++
>  include/dt-bindings/pinctrl/mt6795-pinfunc.h  | 908 ++++++++++++++++++
>  2 files changed, 1132 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pinctrl/mediatek,pinctrl-mt6795.yaml
>  create mode 100644 include/dt-bindings/pinctrl/mt6795-pinfunc.h
> 

...

> +
> +          bias-pull-down:
> +            oneOf:
> +              - type: boolean
> +              - enum: [100, 101, 102, 103]
> +                description: mt6795 pull down PUPD/R0/R1 type define value.
> +            description: |
> +               For normal pull down type, it is not necessary to specify R1R0
> +               values; When pull down type is PUPD/R0/R1, adding R1R0 defines
> +               will set different resistance values.
> +
> +          bias-pull-up:
> +            oneOf:
> +              - type: boolean
> +              - enum: [100, 101, 102, 103]
> +                description: mt6795 pull up PUPD/R0/R1 type define value.
> +            description: |
> +               For normal pull up type, it is not necessary to specify R1R0
> +               values; When pull up type is PUPD/R0/R1, adding R1R0 defines
> +               will set different resistance values.
> +
> +          bias-disable: true
> +
> +          output-high: true
> +
> +          output-low: true
> +
> +          input-enable: true
> +
> +          input-disable: true
> +
> +          input-schmitt-enable: true
> +
> +          input-schmitt-disable: true
> +
> +          mediatek,pull-up-adv:
> +            description: |
> +              Pull up setings for 2 pull resistors, R0 and R1. User can
> +              configure those special pins. Valid arguments are described as below:
> +              0: (R1, R0) = (0, 0) which means R1 disabled and R0 disabled.
> +              1: (R1, R0) = (0, 1) which means R1 disabled and R0 enabled.
> +              2: (R1, R0) = (1, 0) which means R1 enabled and R0 disabled.
> +              3: (R1, R0) = (1, 1) which means R1 enabled and R0 enabled.
> +            $ref: /schemas/types.yaml#/definitions/uint32
> +            enum: [0, 1, 2, 3]
> +
> +          mediatek,pull-down-adv:
> +            description: |
> +              Pull down settings for 2 pull resistors, R0 and R1. User can
> +              configure those special pins. Valid arguments are described as below:
> +              0: (R1, R0) = (0, 0) which means R1 disabled and R0 disabled.
> +              1: (R1, R0) = (0, 1) which means R1 disabled and R0 enabled.
> +              2: (R1, R0) = (1, 0) which means R1 enabled and R0 disabled.
> +              3: (R1, R0) = (1, 1) which means R1 enabled and R0 enabled.
> +            $ref: /schemas/types.yaml#/definitions/uint32
> +            enum: [0, 1, 2, 3]

I'm actually myself trying to figure out why there are two ways of setting
R0/R1 in the dt-binding (and which should preferred for mt8192 and others):
1. passing 0-3 to mediatek,pull-{up,down}-adv
2. passing one of the MTK_PUPD_SET_R1R0_** flags to bias-pull-{up,down}

When the pin is of type MTK_PULL_PUPD_R1R0_TYPE (which should be the only case
in which it makes sense to consider mediatek,pull-{up,down}-adv AFAIU), they end
up doing the same thing, it's:

mtk_pinconf_bias_set_combo() -> mtk_pinconf_bias_set_pupd_r1_r0()
vs
mtk_pinconf_adv_pull_set()

... and they write to the same registers.

Unless I'm missing something here.

Thanks,
Nícolas