linux-kernel - Re: [PATCH v4 2/2] gpio: loongson: add more gpio chip support

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Message-ID: <fd2290b1-66d4-f646-c3c8-b65567eae74a@loongson.cn>
Date:   Tue, 29 Aug 2023 19:27:37 +0800
From:   Yinbo Zhu <zhuyinbo@...ngson.cn>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-gpio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jianmin Lv <lvjianmin@...ngson.cn>, wanghongliang@...ngson.cn,
        loongson-kernel@...ts.loongnix.cn, zhuyinbo@...ngson.cn
Subject: Re: [PATCH v4 2/2] gpio: loongson: add more gpio chip support



在 2023/8/23 下午8:29, Linus Walleij 写道:
> Hi Yinbo,
> 
> thanks for the new patch, it's starting to look really good!
> The main point with offsets in the match data is very nice.
> 
> On Wed, Aug 23, 2023 at 5:34 AM Yinbo Zhu <zhuyinbo@...ngson.cn> wrote:
> 
>> This patch was to add loongson 2k0500, 2k2000 and 3a5000 gpio chip
>> driver support.
>>
>> Signed-off-by: Yinbo Zhu <zhuyinbo@...ngson.cn>
> (...)
> 
> 
>>   static int loongson_gpio_to_irq(struct gpio_chip *chip, unsigned int offset)
>>   {
>> +       unsigned int u;
>>          struct platform_device *pdev = to_platform_device(chip->parent);
>> +       struct loongson_gpio_chip *lgpio = to_loongson_gpio_chip(chip);
>> +
>> +       if (lgpio->chip_data->mode == BIT_CTRL_MODE) {
>> +               u = readl(lgpio->reg_base + lgpio->chip_data->inten_offset + offset / 32 * 4);
>> +               u |= BIT(offset % 32);
>> +               writel(u, lgpio->reg_base + lgpio->chip_data->inten_offset + offset / 32 * 4);
> 
> This offset / 32 * 4 is really hard to read.
> What about
> 
> /* Get the register index from offset then multiply by bytes per register */
> (offset / 32) * 4


okay, I will add it.

> 
>>          lgpio->reg_base = reg_base;
>> +       if (device_property_read_u32(dev, "ngpios", &ngpios) || !ngpios)
>> +               return -EINVAL;
>> +
>> +       ret = DIV_ROUND_UP(ngpios, 8);
>> +       switch (ret) {
>> +       case 1 ... 2:
>> +               io_width = ret;
>> +               break;
>> +       case 3 ... 4:
>> +               io_width = 0x4;
>> +               break;
>> +       case 5 ... 8:
>> +               io_width = 0x8;
>> +               break;
>> +       default:
>> +               dev_err(dev, "unsupported io width\n");
>> +               return -EINVAL;
>> +       }
> 
> Is it really a good idea to infer the register width from ngpios?
> 
> What about just putting this into the struct loongson_gpio_chip_data
> as well? Certainly it will be fixed for a certain device.
> 


Andy's suggestion seems to look better, We have bgpio_init() handle
this switch case. I will remove this switch case.
https://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git/commit/?h=gpio/for-next&id=55b2395e4e92adc492c6b30ac109eb78250dcd9d

Thanks,
Yinbo