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// SPDX-License-Identifier: GPL-2.0
/*
* GPIO latch driver
*
* Copyright (C) 2022 Sascha Hauer <s.hauer@pengutronix.de>
*
* This driver implements a GPIO (or better GPO as there is no input)
* multiplexer based on latches like this:
*
* CLK0 ----------------------. ,--------.
* CLK1 -------------------. `--------|> #0 |
* | | |
* OUT0 ----------------+--|-----------|D0 Q0|-----|<
* OUT1 --------------+-|--|-----------|D1 Q1|-----|<
* OUT2 ------------+-|-|--|-----------|D2 Q2|-----|<
* OUT3 ----------+-|-|-|--|-----------|D3 Q3|-----|<
* OUT4 --------+-|-|-|-|--|-----------|D4 Q4|-----|<
* OUT5 ------+-|-|-|-|-|--|-----------|D5 Q5|-----|<
* OUT6 ----+-|-|-|-|-|-|--|-----------|D6 Q6|-----|<
* OUT7 --+-|-|-|-|-|-|-|--|-----------|D7 Q7|-----|<
* | | | | | | | | | `--------'
* | | | | | | | | |
* | | | | | | | | | ,--------.
* | | | | | | | | `-----------|> #1 |
* | | | | | | | | | |
* | | | | | | | `--------------|D0 Q0|-----|<
* | | | | | | `----------------|D1 Q1|-----|<
* | | | | | `------------------|D2 Q2|-----|<
* | | | | `--------------------|D3 Q3|-----|<
* | | | `----------------------|D4 Q4|-----|<
* | | `------------------------|D5 Q5|-----|<
* | `--------------------------|D6 Q6|-----|<
* `----------------------------|D7 Q7|-----|<
* `--------'
*
* The above is just an example. The actual number of number of latches and
* the number of inputs per latch is derived from the number of GPIOs given
* in the corresponding device tree properties.
*/
#include <common.h>
#include <errno.h>
#include <io.h>
#include <of.h>
#include <gpio.h>
#include <init.h>
#include <of_gpio.h>
#include <linux/bitmap.h>
struct gpio_latch_priv {
struct gpio_chip gc;
int *clk_gpios;
int *latched_gpios;
int n_latched_gpios;
unsigned int setup_duration_ns;
unsigned int clock_duration_ns;
unsigned long *shadow;
};
static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset)
{
return 0;
}
static void gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val)
{
struct gpio_latch_priv *priv = container_of(gc, struct gpio_latch_priv, gc);
int latch = offset / priv->n_latched_gpios;
int i;
assign_bit(offset, priv->shadow, val);
for (i = 0; i < priv->n_latched_gpios; i++)
gpio_set_value(priv->latched_gpios[i],
test_bit(latch * priv->n_latched_gpios + i, priv->shadow));
ndelay(priv->setup_duration_ns);
gpio_set_value(priv->clk_gpios[latch], 1);
ndelay(priv->clock_duration_ns);
gpio_set_value(priv->clk_gpios[latch], 0);
}
static int gpio_latch_direction_output(struct gpio_chip *gc, unsigned gpio, int val)
{
gpio_latch_set(gc, gpio, val);
return 0;
}
#define DURATION_NS_MAX 5000
static struct gpio_ops gpio_latch_gpio_ops = {
.direction_output = gpio_latch_direction_output,
.set = gpio_latch_set,
.get_direction = gpio_latch_get_direction,
};
static int gpio_latch_probe(struct device_d *dev)
{
struct gpio_latch_priv *priv;
int n_latches, i, ret;
struct device_node *np = dev->device_node;
enum of_gpio_flags flags;
priv = xzalloc(sizeof(*priv));
n_latches = of_gpio_named_count(np, "clk-gpios");
if (n_latches < 0) {
dev_err(dev, "invalid or missing clk-gpios");
ret = -EINVAL;
goto err_gpio;
}
priv->n_latched_gpios = of_gpio_named_count(np, "latched-gpios");
if (priv->n_latched_gpios < 0) {
dev_err(dev, "invalid or missing latched-gpios");
ret = -EINVAL;
goto err_gpio;
}
priv->clk_gpios = xzalloc(sizeof(int) * n_latches);
priv->latched_gpios = xzalloc(sizeof(int) * priv->n_latched_gpios);
for (i = 0; i < n_latches; i++) {
priv->clk_gpios[i] = of_get_named_gpio_flags(np, "clk-gpios",
i, &flags);
ret = gpio_request_one(priv->clk_gpios[i],
flags & OF_GPIO_ACTIVE_LOW ? GPIOF_ACTIVE_LOW : 0,
dev_name(dev));
if (ret) {
dev_err(dev, "Cannot request gpio %d: %s\n", priv->clk_gpios[i],
strerror(-ret));
goto err_gpio;
}
gpio_direction_output(priv->clk_gpios[i], 0);
}
for (i = 0; i < priv->n_latched_gpios; i++) {
priv->latched_gpios[i] = of_get_named_gpio_flags(np, "latched-gpios",
i, &flags);
ret = gpio_request_one(priv->latched_gpios[i],
flags & OF_GPIO_ACTIVE_LOW ? GPIOF_ACTIVE_LOW : 0,
dev_name(dev));
if (ret) {
dev_err(dev, "Cannot request gpio %d: %s\n", priv->latched_gpios[i],
strerror(-ret));
goto err_gpio;
}
}
priv->shadow = bitmap_zalloc(n_latches * priv->n_latched_gpios);
of_property_read_u32(np, "setup-duration-ns", &priv->setup_duration_ns);
if (priv->setup_duration_ns > DURATION_NS_MAX) {
dev_warn(dev, "setup-duration-ns too high, limit to %d\n",
DURATION_NS_MAX);
priv->setup_duration_ns = DURATION_NS_MAX;
}
of_property_read_u32(np, "clock-duration-ns", &priv->clock_duration_ns);
if (priv->clock_duration_ns > DURATION_NS_MAX) {
dev_warn(dev, "clock-duration-ns too high, limit to %d\n",
DURATION_NS_MAX);
priv->clock_duration_ns = DURATION_NS_MAX;
}
priv->gc.ops = &gpio_latch_gpio_ops;
priv->gc.ngpio = n_latches * priv->n_latched_gpios;
priv->gc.base = -1;
priv->gc.dev = dev;
return gpiochip_add(&priv->gc);
err_gpio:
return ret;
}
static const struct of_device_id gpio_latch_ids[] = {
{
.compatible = "gpio-latch",
}, {
/* sentinel */
}
};
static struct driver_d gpio_latch_driver = {
.name = "gpio-latch",
.probe = gpio_latch_probe,
.of_compatible = DRV_OF_COMPAT(gpio_latch_ids),
};
device_platform_driver(gpio_latch_driver);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
MODULE_DESCRIPTION("GPIO latch driver");
|
