linux-kernel - Re: [PATCH] gpio: add Intel WhiskeyCove GPIO driver

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Date:	Mon, 13 Jun 2016 14:43:16 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Bin Gao <bin.gao@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ajay Thomas <ajay.thomas.david.rajamanickam@...el.com>,
	Bin Gao <bin.gao@...el.com>
Subject: Re: [PATCH] gpio: add Intel WhiskeyCove GPIO driver

On Sat, Jun 11, 2016 at 8:01 AM, Bin Gao <bin.gao@...ux.intel.com> wrote:

> This patch introduces a separate GPIO driver for Intel WhiskeyCove PMIC.
> This driver is based on gpio-crystalcove.c.
>
> Signed-off-by: Ajay Thomas <ajay.thomas.david.rajamanickam@...el.com>
> Signed-off-by: Bin Gao <bin.gao@...el.com>

It is always good to let Mika and Mathias look at new Intel GPIO
drivers, so added them to the To: line.

> +config GPIO_WHISKEY_COVE
> +       tristate "GPIO support for Whiskey Cove PMIC"
> +       depends on INTEL_SOC_PMIC
> +       select GPIOLIB_IRQCHIP
> +       help
> +         Support for GPIO pins on Whiskey Cove PMIC.
> +
> +         Say Yes if you have a Intel SoC based tablet with Whsikey Cove PMIC

Speling

> +#include <linux/interrupt.h>
> +#include <linux/platform_device.h>
> +#include <linux/gpio.h>

No use just #include <linux/gpio/driver.h>

> +#include <linux/seq_file.h>
> +#include <linux/bitops.h>
> +#include <linux/regmap.h>
> +#include <linux/mfd/intel_soc_pmic.h>
> +
> +#define WCOVE_GPIO_NUM 13
> +#define WCOVE_VGPIO_NUM        94
> +
> +#define UPDATE_IRQ_TYPE                BIT(0)
> +#define UPDATE_IRQ_MASK                BIT(1)
> +
> +#define GPIOIRQ0               0x4e0b
> +#define GPIOIRQ1               0x4e0c
> +#define MGPIOIRQ0              0x4e19
> +#define MGPIOIRQ1              0x4e1a
> +#define GPIO0P0CTLO            0x4e44
> +#define GPIO0P0CTLI            0x4e51
> +#define GPIO1P0CTLO            0x4e4b
> +#define GPIO1P0CTLI            0x4e58
> +#define GPIO2P0CTLO            0x4e4f
> +#define GPIO2P0CTLI            0x4e5c
> +
> +#define CTLI_INTCNT_DIS                (0)
> +#define CTLI_INTCNT_NE         (1 << 1)
> +#define CTLI_INTCNT_PE         (2 << 1)
> +#define CTLI_INTCNT_BE         (3 << 1)
> +
> +#define CTLO_DIR_IN            (0)
> +#define CTLO_DIR_OUT           (1 << 5)
> +
> +#define CTLO_DRV_CMOS          (0)
> +#define CTLO_DRV_OD            (1 << 4)

That is likely what we call push-pull and open drain driving.
Implement .set_single_ended() for this driver so you can handle
that properly in the driver.

> +#define CTLO_DRV_REN           (1 << 3)
> +
> +#define CTLO_RVAL_2KDW         (0)
> +#define CTLO_RVAL_2KUP         (1 << 1)
> +#define CTLO_RVAL_50KDW                (2 << 1)
> +#define CTLO_RVAL_50KUP                (3 << 1)

Looks like pull-up settings. That is strictly speaking pin control.

But OK I am trying to find the right way to abstract this without
making GPIO too heavyweight.

> +static inline struct wcove_gpio *to_wg(struct gpio_chip *gc)
> +{
> +       return container_of(gc, struct wcove_gpio, chip);
> +}

No don't do that. Use devm_gpiochip_add_data() and just
use gpiochip_get_data() to get the pointer out. Look at any
other driver in the upstream kernel, I think I converted them all.

> +static inline int to_reg(int gpio, enum ctrl_register reg_type)
> +{
> +       int reg;
> +
> +       if (reg_type == CTRL_IN) {
> +               if (gpio < 7)
> +                       reg = GPIO0P0CTLI + gpio;
> +               else if (gpio < 11)
> +                       reg = GPIO1P0CTLI + (gpio % 7);
> +               else
> +                       reg = GPIO2P0CTLI + (gpio % 11);
> +       } else {
> +               if (gpio < 7)
> +                       reg = GPIO0P0CTLO + gpio;
> +               else if (gpio < 11)
> +                       reg = GPIO1P0CTLO + (gpio % 7);
> +               else
> +                       reg = GPIO2P0CTLO + (gpio % 11);
> +       }
> +
> +       return reg;
> +}

You could add a kerneldoc to this function explaining how these
GPIO registers are laid out.

> +static void wcove_gpio_set(struct gpio_chip *chip,
> +                                unsigned int gpio, int value)
> +{
> +       struct wcove_gpio *wg = to_wg(chip);
> +
> +       if (gpio > WCOVE_VGPIO_NUM)
> +               return;

gpiolib already protects against this, you can drop it everywhere.

> +static irqreturn_t wcove_gpio_irq_handler(int irq, void *data)
> +{
> +       struct wcove_gpio *wg = data;
> +       unsigned int p0, p1, virq;
> +       int pending, gpio;
> +
> +       if (regmap_read(wg->regmap, GPIOIRQ0, &p0) ||
> +           regmap_read(wg->regmap, GPIOIRQ1, &p1))
> +               return IRQ_NONE;

What does this mean? If we fail to read regmaps then
it was not our IRQ?

Should be an error message or something at least I think?

Apart from that it looks all right.

Yours,
Linus Walleij