linux-kernel - Re: [PATCH] gpio: lp87565: Add support for GPIO

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Date:   Sun, 11 Jun 2017 09:57:02 +0530
From:   Keerthy <j-keerthy@...com>
To:     Linus Walleij <linus.walleij@...aro.org>
CC:     Lee Jones <lee.jones@...aro.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Tero Kristo <t-kristo@...com>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Andrew F. Davis" <afd@...com>
Subject: Re: [PATCH] gpio: lp87565: Add support for GPIO



On Friday 09 June 2017 02:06 PM, Linus Walleij wrote:
> On Thu, Jun 1, 2017 at 5:10 AM, Keerthy <j-keerthy@...com> wrote:
> 
>> Add driver for lp87565 PMIC family GPIOs. Three GPIOs are supported
>> and can be configured in Open-drain output or Push-pull output.
>>
>> Signed-off-by: Keerthy <j-keerthy@...com>
> 
> (...)
>> The latest version of mfd driver for this pmic is posted:
>> https://lkml.org/lkml/2017/5/30/463
> (...)
>> +config GPIO_LP87565
>> +       tristate "TI LP87565 GPIO"
>> +       depends on MFD_TI_LP87565
> 
> Hm I guess that means I could merge it since it will only compile once
> that symbol turns up in the kernel tree.

Yes.

> 
>> +#include <linux/gpio.h>
> 
> Please use
> #include <linux/gpio/driver.h>
> only.

Okay

> 
>> +#include <linux/mfd/lp87565.h>
> 
> Is this API stable enough that I could merge this and count on it to
> "just work" once the MFD driver lands?
> 
>> +struct lp87565_gpio {
>> +       struct gpio_chip chip;
>> +       struct lp87565 *lp87565;
>> +};
> 
> It seems the code would be easier to read if you store the struct regmap *map
> pointer here instead of the whole struct lp87565.
> 
> But it's no strong preference.

Okay

> 
>> +static int lp87565_gpio_get(struct gpio_chip *chip, unsigned int offset)
>> +{
>> +       struct lp87565_gpio *gpio = gpiochip_get_data(chip);
>> +       int ret, val;
>> +
>> +       ret = regmap_read(gpio->lp87565->regmap, LP87565_REG_GPIO_IN, &val);
>> +       if (ret < 0)
>> +               return ret;
>> +
>> +       return val & BIT(offset);
> 
> return !!(val & BIT(offset));
> 
> please, so it's clear that we clamp to [0,1].

Okay

> 
>> +static int lp87565_gpio_request(struct gpio_chip *gc, unsigned int offset)
>> +{
>> +       struct lp87565_gpio *gpio = gpiochip_get_data(gc);
>> +       int ret;
>> +
>> +       switch (offset) {
>> +       case 0:
>> +       case 1:
>> +       case 2:
>> +               /* Setup the GPIO*_SEL MUX to GPIO mode */
>> +               ret = regmap_update_bits(gpio->lp87565->regmap,
>> +                                        LP87565_REG_PIN_FUNCTION,
>> +                                        BIT(offset), BIT(offset));
> 
> Hm. Hm.
> 
> If this IC has several function modes for the pins it should also
> be a pin controller... I know it is a lot of upfront code, but... it will
> benefit you in the long run. Is it really just these three pins?
> 
> Maybe we should merge it into
> drivers/pinctrl/pinctrl-lp87565.c so that at least file placement does
> not become a problem later?

No Linus. Only 2 modes. So went along the lines of
drivers/gpio/gpio-lp873x.c. If you are not okay with this. I can as well
remove this part.

> 
>> +static int lp87565_gpio_set_config(struct gpio_chip *gc, unsigned int offset,
>> +                                  unsigned long config)
>> +{
>> +       struct lp87565_gpio *gpio = gpiochip_get_data(gc);
>> +
>> +       switch (pinconf_to_config_param(config)) {
>> +       case PIN_CONFIG_DRIVE_OPEN_DRAIN:
>> +               return regmap_update_bits(gpio->lp87565->regmap,
>> +                                         LP87565_REG_GPIO_CONFIG,
>> +                                         BIT(offset +
>> +                                             __ffs(LP87565_GOIO1_OD)),
>> +                                         BIT(offset +
>> +                                             __ffs(LP87565_GOIO1_OD)));
>> +       case PIN_CONFIG_DRIVE_PUSH_PULL:
>> +               return regmap_update_bits(gpio->lp87565->regmap,
>> +                                         LP87565_REG_GPIO_CONFIG,
>> +                                         BIT(offset +
>> +                                             __ffs(LP87565_GOIO1_OD)), 0);
>> +       default:
>> +               return -ENOTSUPP;
>> +       }
>> +}
> 
> Nice.
> 
> If this was a split GPIO+pin control driver this would just be a call
> into the pinctrl back-end from the GPIO controller, like
> drivers/pinctrl/intel/pinctrl-intel.c does with just using
> gpiochip_generic_config().

okay. These are the two modes. Do you prefer have the driver split. I
took the reference of lp873x and tps65218. So let me know.

> 
>> +static int lp87565_gpio_probe(struct platform_device *pdev)
>> +{
>> +       struct lp87565_gpio *gpio;
>> +       int ret;
>> +
>> +       gpio = devm_kzalloc(&pdev->dev, sizeof(*gpio), GFP_KERNEL);
>> +       if (!gpio)
>> +               return -ENOMEM;
>> +
>> +       platform_set_drvdata(pdev, gpio);
> 
> Is this pointer used anywhere?

Actually no. I can remove this.

> 
>> +       gpio->lp87565 = dev_get_drvdata(pdev->dev.parent);
> 
> So maybe assign the regmap instead.

Sure. Seems that is the only thing i am using out of the lp87565
structure. I will do that.

> 
> Yours,
> Linus Walleij
>