linux-kernel - Re: [PATCH v2 02/13] dt-bindings: pinctrl: renesas: Document RZ/V2H(P) SoC

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Message-ID: <CAMuHMdV+oVFNUJse0th_PXKhtsUzXa7Mk7ozq5cKZoYX12AMRw@mail.gmail.com>
Date: Wed, 24 Apr 2024 11:05:58 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Magnus Damm <magnus.damm@...il.com>, linux-renesas-soc@...r.kernel.org, 
	linux-gpio@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v2 02/13] dt-bindings: pinctrl: renesas: Document
 RZ/V2H(P) SoC

Hi Prabhakar,

Thanks for your patch!

On Tue, Apr 23, 2024 at 7:59 PM Prabhakar <prabhakar.csengg@...il.com> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> Add documentation for the pin controller found on the Renesas RZ/V2H(P)
> (R9A09G057) SoC. The RZ/V2H PFC varies slightly compared to the RZ/G2L
> family:
> - Additional bits need to be set during pinmuxing.
> - The GPIO pin count is different.
>
> Hence, a SoC-specific compatible string, 'renesas,r9a09g057-pinctrl', is
> added for the RZ/V2H(P) SoC.
>
> Also, add the 'renesas,output-impedance' property. The drive strength
> setting on RZ/V2H(P) depends on the different power rails coming out from
> the PMIC (connected via I2C). These power rails (required for drive
> strength) can be 1.2V, 1.8V, or 3.3V.
>
> Pins are grouped into 4 groups:
>
> Group 1: Impedance
> - 150/75/38/25 ohms (at 3.3V)
> - 130/65/33/22 ohms (at 1.8V)
>
> Group 2: Impedance
> - 50/40/33/25 ohms (at 1.8V)
>
> Group 3: Impedance
> - 150/75/37.5/25 ohms (at 3.3V)
> - 130/65/33/22 ohms (at 1.8V)
>
> Group 4: Impedance
> - 110/55/30/20 ohms (at 1.8V)
> - 150/75/38/25 ohms (at 1.2V)
>
> The 'renesas,output-impedance' property, as documented, can be
> [0, 1, 2, 3], indicating x1/x2/x3/x4 drive strength.

The documentation says "x1/x2/x4/x6" for all but Group 4 (P20/P21).
Still, the actual values don't seem to match the magnification factors...

> As power rail information may not be available very early in the boot
> process, the 'renesas,output-impedance' property is added instead of
> reusing the 'output-impedance-ohms' property.
>
> Also, allow bias-disable, bias-pull-down and bias-pull-up properties
> as these can be used to configure the pins.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

> --- a/Documentation/devicetree/bindings/pinctrl/renesas,rzg2l-pinctrl.yaml
> +++ b/Documentation/devicetree/bindings/pinctrl/renesas,rzg2l-pinctrl.yaml
> @@ -111,6 +116,18 @@ additionalProperties:
>          output-high: true
>          output-low: true
>          line-name: true
> +        bias-disable: true
> +        bias-pull-down: true
> +        bias-pull-up: true
> +        renesas,output-impedance:
> +          description: |
> +            Output impedance for pins on RZ/V2H(P) SoC.
> +            0: Corresponds to x1
> +            1: Corresponds to x2
> +            2: Corresponds to x3
> +            3: Corresponds to x4

Hence I'd drop the multiplication factors, and just say the meaning
of the value is pin-dependent?

> +          $ref: /schemas/types.yaml#/definitions/uint32
> +          enum: [0, 1, 2, 3]
>
>      - type: object
>        additionalProperties:

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds