Message-ID: <Z5LOdh-4UxRtteOy@chonkvm.lixom.net>
Date: Thu, 23 Jan 2025 15:19:18 -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

On Thu, Jan 23, 2025 at 11:30:42AM +0000, Yixun Lan wrote:
> Hi Olof:
>  thanks for your reivew
> 
> On 12:03 Wed 22 Jan     , Olof Johansson wrote:
> > 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,.
> > 
> yes, all ports share same interrupt line, but each port has its own
> irq related handling register, so it make sense to describe as per gpio irqchip
> 
> also see comments below
> 
> > > +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
> how to handle the fourth gpio port? I would like to have uniform driver for all ports
> 
> > 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.
> > 
> 
> IIUC, your suggestion here was same as the implementation of patch v3 of this driver[1],
>  while combining all four ports into one irqchip, which NACKed by maintainer[2].
>  I tend to agree having a gpio-controller per bank provide more flexibility,
>  easy to leverage generic gpio framework, even each port can be disabled or enabled,
>  and IMO having shared irq handler isn't really a problem..
> 
> [1] https://lore.kernel.org/r/20241225-03-k1-gpio-v3-0-27bb7b441d62@gentoo.org
> [2] https://lore.kernel.org/r/CACRpkdZPD2C2iPwOX_kW1Ug8jVkdHhhc7iFycHtzj5LQ0XWNgQ@mail.gmail.com
> https://lore.kernel.org/r/CACRpkdYgGho=VQabonq4HccEiXBH2qM76K45oDaV1Jyi0xZ-YA@mail.gmail.com

Hmm, I don't understand the reasoning there, but it's not my subsystem.

It seems worse to me to misdescribe the hardware as separate blocks
with a device-tree binding that no longer describes the actual hardware,
but it's not up to me.

Let's get the platform support merged, ignore my feedback here -- we need more
SoCs supported upstream and this code is good enough to go in as-is.


-Olof

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