linux-kernel - Re: [PATCH v4 1/4] dt-bindings: gpio: spacemit: add support for K1 SoC

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Message-ID: <Z5FPJLzAEVXGWJnE@chonkvm.lixom.net>
Date: Wed, 22 Jan 2025 12:03:48 -0800
From: Olof Johansson <olof@...om.net>
To: Yixun Lan <dlan@...too.org>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Conor Dooley <conor@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>, Yangyu Chen <cyy@...self.name>,
	Jisheng Zhang <jszhang@...nel.org>,
	Jesse Taube <mr.bossman075@...il.com>,
	Inochi Amaoto <inochiama@...look.com>,
	Icenowy Zheng <uwu@...nowy.me>,
	Meng Zhang <zhangmeng.kevin@...ux.spacemit.com>,
	linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v4 1/4] dt-bindings: gpio: spacemit: add support for K1
 SoC

Hi,

On Tue, Jan 21, 2025 at 11:38:11AM +0800, Yixun Lan wrote:
> The GPIO controller of K1 support basic functions as input/output,
> all pins can be used as interrupt which route to one IRQ line,
> trigger type can be select between rising edge, failing edge, or both.
> There are four GPIO ports, each consisting of 32 pins.
> 
> Signed-off-by: Yixun Lan <dlan@...too.org>
> ---
>  .../devicetree/bindings/gpio/spacemit,k1-gpio.yaml | 116 +++++++++++++++++++++
>  1 file changed, 116 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/gpio/spacemit,k1-gpio.yaml b/Documentation/devicetree/bindings/gpio/spacemit,k1-gpio.yaml
> new file mode 100644
> index 0000000000000000000000000000000000000000..dd9459061aecfcba84e6a3c5052fbcddf6c61150
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/gpio/spacemit,k1-gpio.yaml
> @@ -0,0 +1,116 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/gpio/spacemit,k1-gpio.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: SpacemiT K1 GPIO controller
> +
> +maintainers:
> +  - Yixun Lan <dlan@...too.org>
> +
> +description:
> +  The controller's registers are organized as sets of eight 32-bit
> +  registers with each set of port controlling 32 pins.  A single
> +  interrupt line is shared for all of the pins by the controller.
> +  Each port will be represented as child nodes with the generic
> +  GPIO-controller properties in this bindings file.

There's only one interrupt line for all ports, but you have a binding that
duplicates them for every set of ports. That seems overly complicated,
doesn't it? They'd all bind the same handler, so there's no benefit in
providing the flexibility,.

> +properties:
> +  $nodename:
> +    pattern: "^gpio@[0-9a-f]+$"
> +
> +  compatible:
> +    const: spacemit,k1-gpio
> +
> +  reg:
> +    maxItems: 1
> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 0
> +
> +patternProperties:
> +  "^gpio-port@[0-9a-f]+$":
> +    type: object
> +    properties:
> +      compatible:
> +        const: spacemit,k1-gpio-port
> +
> +      reg:
> +        maxItems: 1
> +
> +      gpio-controller: true
> +
> +      "#gpio-cells":
> +        const: 2
> +
> +      gpio-ranges: true
> +
> +      interrupts:
> +        maxItems: 1
> +
> +      interrupt-controller: true
> +
> +      "#interrupt-cells":
> +        const: 2
> +        description:
> +          The first cell is the GPIO number, the second should specify interrupt
> +          flag. The controller does not support level interrupts, so flags of
> +          IRQ_TYPE_LEVEL_HIGH, IRQ_TYPE_LEVEL_LOW should not be used.
> +          Refer <dt-bindings/interrupt-controller/irq.h> for valid flags.

Same here, since there's no real flexibility between the banks, it might
make sense to consider a 3-cell GPIO specifier instead, and having
the first cell indicate bank. I could see this argument go in either
direction, but I'm not sure I understand why to provide a gpio-controller
per bank.

Comparing to say Rockchip, where each bank has a separate interrupt line
-- so there the granularity makes sense.


-Olof