linux-kernel - Re: [PATCH v2 1/4] dt-bindings: aspeed-sgpio: Convert txt bindings to yaml.

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Date:   Fri, 28 May 2021 12:09:34 +0800
From:   Steven Lee <steven_lee@...eedtech.com>
To:     Linus Walleij <linus.walleij@...aro.org>
CC:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:ARM/ASPEED MACHINE SUPPORT" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/ASPEED MACHINE SUPPORT" 
        <linux-aspeed@...ts.ozlabs.org>,
        open list <linux-kernel@...r.kernel.org>,
        Hongwei Zhang <Hongweiz@....com>,
        Ryan Chen <ryan_chen@...eedtech.com>,
        Billy Tsai <billy_tsai@...eedtech.com>
Subject: Re: [PATCH v2 1/4] dt-bindings: aspeed-sgpio: Convert txt bindings
 to yaml.

The 05/28/2021 07:51, Linus Walleij wrote:
> On Thu, May 27, 2021 at 2:55 AM Steven Lee <steven_lee@...eedtech.com> wrote:
> 
> > SGPIO bindings should be converted as yaml format.
> > In addition to the file conversion, a new property max-ngpios is
> > added in the yaml file as well.
> > The new property is required by the enhanced sgpio driver for
> > making the configuration of the max number of gpio pins more flexible.
> >
> > Signed-off-by: Steven Lee <steven_lee@...eedtech.com>
> (...)
> > +  max-ngpios:
> > +    description:
> > +      represents the number of actual hardware-supported GPIOs (ie,
> > +      slots within the clocked serial GPIO data). Since each HW GPIO is both an
> > +      input and an output, we provide max_ngpios * 2 lines on our gpiochip
> > +      device. We also use it to define the split between the inputs and
> > +      outputs; the inputs start at line 0, the outputs start at max_ngpios.
> > +    minimum: 0
> > +    maximum: 128
> 
> Why can this not be derived from the compatible value?
> 
> Normally there should be one compatible per hardware variant
> of the block. And this should be aligned with that, should it not?
> 
> If this is not the case, maybe more detailed compatible strings
> are needed, maybe double compatibles with compatible per
> family and SoC?
> 

Thanks for your suggestion.
I add max-ngpios in dt-bindings as there is ngpios defined in
dt-bindings, users can get the both max-ngpios and ngpios information
from dtsi without digging sgpio driver.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/aspeed-g5.dtsi#n354

If adding more detailed compatibles is better, I will add them to sgpio driver
in V3 patch and remove max-ngpios from dt-bindings.

Since AST2600 has 2 sgpio controller one with 128 pins and another one with 80 pins.
For supporting max-ngpios in compatibles, 2 platform data for each
ast2600 sgpio controller as follows are necessary.

```
static const struct aspeed_sgpio_pdata ast2600_sgpiom1_pdata = {
        .max_ngpios = 128;
};
static const struct aspeed_sgpio_pdata ast2600_sgpiom2_pdata = {
        .max_ngpios = 80;
};

{ .compatible = "aspeed,ast2500-sgpio" , .data = &ast2400_sgpio_pdata, },
{ .compatible = "aspeed,ast2600-sgpiom1", .data = &ast2600_sgpiom1_pdata, },
{ .compatible = "aspeed,ast2600-sgpiom2", .data = &ast2600_sgpiom2_pdata, },
```

Thanks,
Steven

> Yours,
> Linus Walleij