gpio: add generic single-register fixed-direction GPIO driver

Add a simple, generic, single register fixed-direction GPIO driver.
This is able to support a single register with a mixture of inputs
and outputs.

This is different from gpio-mmio and gpio-74xx-mmio:
* gpio-mmio doesn't allow a fixed direction, it assumes there is always
  a direction register.
* gpio-74xx-mmio only supports all-in or all-out setups
* gpio-74xx-mmio is DT only, this needs to support legacy too
* they don't double-read when getting the GPIO value, as required by
  some implementations that this driver supports
* we need to always do 32-bit reads, which bgpio doesn't guarantee
* the current output state may not be readable from the hardware
  register - reading may reflect input status but not output status.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Russell King 2016-08-31 08:49:44 +01:00 committed by Linus Walleij
parent c65d1fd350
commit 380639c7cc
4 changed files with 183 additions and 0 deletions

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@ -380,6 +380,12 @@ config GPIO_RCAR
help
Say yes here to support GPIO on Renesas R-Car SoCs.
config GPIO_REG
bool
help
A 32-bit single register GPIO fixed in/out implementation. This
can be used to represent any register as a set of GPIO signals.
config GPIO_SPEAR_SPICS
bool "ST SPEAr13xx SPI Chip Select as GPIO support"
depends on PLAT_SPEAR

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@ -98,6 +98,7 @@ obj-$(CONFIG_GPIO_PXA) += gpio-pxa.o
obj-$(CONFIG_GPIO_RC5T583) += gpio-rc5t583.o
obj-$(CONFIG_GPIO_RDC321X) += gpio-rdc321x.o
obj-$(CONFIG_GPIO_RCAR) += gpio-rcar.o
obj-$(CONFIG_GPIO_REG) += gpio-reg.o
obj-$(CONFIG_ARCH_SA1100) += gpio-sa1100.o
obj-$(CONFIG_GPIO_SCH) += gpio-sch.o
obj-$(CONFIG_GPIO_SCH311X) += gpio-sch311x.o

164
drivers/gpio/gpio-reg.c Normal file
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@ -0,0 +1,164 @@
/*
* gpio-reg: single register individually fixed-direction GPIOs
*
* Copyright (C) 2016 Russell King
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*/
#include <linux/gpio/driver.h>
#include <linux/gpio/gpio-reg.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
struct gpio_reg {
struct gpio_chip gc;
spinlock_t lock;
u32 direction;
u32 out;
void __iomem *reg;
};
#define to_gpio_reg(x) container_of(x, struct gpio_reg, gc)
static int gpio_reg_get_direction(struct gpio_chip *gc, unsigned offset)
{
struct gpio_reg *r = to_gpio_reg(gc);
return r->direction & BIT(offset) ? 1 : 0;
}
static int gpio_reg_direction_output(struct gpio_chip *gc, unsigned offset,
int value)
{
struct gpio_reg *r = to_gpio_reg(gc);
if (r->direction & BIT(offset))
return -ENOTSUPP;
gc->set(gc, offset, value);
return 0;
}
static int gpio_reg_direction_input(struct gpio_chip *gc, unsigned offset)
{
struct gpio_reg *r = to_gpio_reg(gc);
return r->direction & BIT(offset) ? 0 : -ENOTSUPP;
}
static void gpio_reg_set(struct gpio_chip *gc, unsigned offset, int value)
{
struct gpio_reg *r = to_gpio_reg(gc);
unsigned long flags;
u32 val, mask = BIT(offset);
spin_lock_irqsave(&r->lock, flags);
val = r->out;
if (value)
val |= mask;
else
val &= ~mask;
r->out = val;
writel_relaxed(val, r->reg);
spin_unlock_irqrestore(&r->lock, flags);
}
static int gpio_reg_get(struct gpio_chip *gc, unsigned offset)
{
struct gpio_reg *r = to_gpio_reg(gc);
u32 val, mask = BIT(offset);
if (r->direction & mask) {
/*
* double-read the value, some registers latch after the
* first read.
*/
readl_relaxed(r->reg);
val = readl_relaxed(r->reg);
} else {
val = r->out;
}
return !!(val & mask);
}
static void gpio_reg_set_multiple(struct gpio_chip *gc, unsigned long *mask,
unsigned long *bits)
{
struct gpio_reg *r = to_gpio_reg(gc);
unsigned long flags;
spin_lock_irqsave(&r->lock, flags);
r->out = (r->out & ~*mask) | (*bits & *mask);
writel_relaxed(r->out, r->reg);
spin_unlock_irqrestore(&r->lock, flags);
}
/**
* gpio_reg_init - add a fixed in/out register as gpio
* @dev: optional struct device associated with this register
* @base: start gpio number, or -1 to allocate
* @num: number of GPIOs, maximum 32
* @label: GPIO chip label
* @direction: bitmask of fixed direction, one per GPIO signal, 1 = in
* @def_out: initial GPIO output value
* @names: array of %num strings describing each GPIO signal
*
* Add a single-register GPIO device containing up to 32 GPIO signals,
* where each GPIO has a fixed input or output configuration. Only
* input GPIOs are assumed to be readable from the register, and only
* then after a double-read. Output values are assumed not to be
* readable.
*/
struct gpio_chip *gpio_reg_init(struct device *dev, void __iomem *reg,
int base, int num, const char *label, u32 direction, u32 def_out,
const char *const *names)
{
struct gpio_reg *r;
int ret;
if (dev)
r = devm_kzalloc(dev, sizeof(*r), GFP_KERNEL);
else
r = kzalloc(sizeof(*r), GFP_KERNEL);
if (!r)
return ERR_PTR(-ENOMEM);
spin_lock_init(&r->lock);
r->gc.label = label;
r->gc.get_direction = gpio_reg_get_direction;
r->gc.direction_input = gpio_reg_direction_input;
r->gc.direction_output = gpio_reg_direction_output;
r->gc.set = gpio_reg_set;
r->gc.get = gpio_reg_get;
r->gc.set_multiple = gpio_reg_set_multiple;
r->gc.base = base;
r->gc.ngpio = num;
r->gc.names = names;
r->direction = direction;
r->out = def_out;
r->reg = reg;
if (dev)
ret = devm_gpiochip_add_data(dev, &r->gc, r);
else
ret = gpiochip_add_data(&r->gc, r);
return ret ? ERR_PTR(ret) : &r->gc;
}
int gpio_reg_resume(struct gpio_chip *gc)
{
struct gpio_reg *r = to_gpio_reg(gc);
unsigned long flags;
spin_lock_irqsave(&r->lock, flags);
writel_relaxed(r->out, r->reg);
spin_unlock_irqrestore(&r->lock, flags);
return 0;
}

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@ -0,0 +1,12 @@
#ifndef GPIO_REG_H
#define GPIO_REG_H
struct device;
struct gpio_chip *gpio_reg_init(struct device *dev, void __iomem *reg,
int base, int num, const char *label, u32 direction, u32 def_out,
const char *const *names);
int gpio_reg_resume(struct gpio_chip *gc);
#endif