linux-stable/drivers/media/rc/gpio-ir-tx.c
Sean Young 1451b93223 media: gpio-ir-tx: spinlock is not needed to disable interrupts
During bit-banging the IR on a gpio pin, we cannot be scheduled or have
anything interrupt us, else the generated signal will be incorrect.
Therefore, we need to disable interrupts on the local cpu. This also
disables preemption.

local_irq_disable() does exactly what we need and does not require a
spinlock.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
2020-08-28 14:06:36 +02:00

193 lines
4.3 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2017 Sean Young <sean@mess.org>
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/gpio/consumer.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <media/rc-core.h>
#define DRIVER_NAME "gpio-ir-tx"
#define DEVICE_NAME "GPIO IR Bit Banging Transmitter"
struct gpio_ir {
struct gpio_desc *gpio;
unsigned int carrier;
unsigned int duty_cycle;
};
static const struct of_device_id gpio_ir_tx_of_match[] = {
{ .compatible = "gpio-ir-tx", },
{ },
};
MODULE_DEVICE_TABLE(of, gpio_ir_tx_of_match);
static int gpio_ir_tx_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
{
struct gpio_ir *gpio_ir = dev->priv;
gpio_ir->duty_cycle = duty_cycle;
return 0;
}
static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier)
{
struct gpio_ir *gpio_ir = dev->priv;
if (carrier > 500000)
return -EINVAL;
gpio_ir->carrier = carrier;
return 0;
}
static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
uint count)
{
ktime_t edge;
s32 delta;
int i;
local_irq_disable();
edge = ktime_get();
for (i = 0; i < count; i++) {
gpiod_set_value(gpio_ir->gpio, !(i % 2));
edge = ktime_add_us(edge, txbuf[i]);
delta = ktime_us_delta(edge, ktime_get());
if (delta > 0)
udelay(delta);
}
gpiod_set_value(gpio_ir->gpio, 0);
}
static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
uint count)
{
ktime_t edge;
/*
* delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
* m68k ndelay(s64) does not compile; so use s32 rather than s64.
*/
s32 delta;
int i;
unsigned int pulse, space;
/* Ensure the dividend fits into 32 bit */
pulse = DIV_ROUND_CLOSEST(gpio_ir->duty_cycle * (NSEC_PER_SEC / 100),
gpio_ir->carrier);
space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
(NSEC_PER_SEC / 100), gpio_ir->carrier);
local_irq_disable();
edge = ktime_get();
for (i = 0; i < count; i++) {
if (i % 2) {
// space
edge = ktime_add_us(edge, txbuf[i]);
delta = ktime_us_delta(edge, ktime_get());
if (delta > 0)
udelay(delta);
} else {
// pulse
ktime_t last = ktime_add_us(edge, txbuf[i]);
while (ktime_before(ktime_get(), last)) {
gpiod_set_value(gpio_ir->gpio, 1);
edge = ktime_add_ns(edge, pulse);
delta = ktime_to_ns(ktime_sub(edge,
ktime_get()));
if (delta > 0)
ndelay(delta);
gpiod_set_value(gpio_ir->gpio, 0);
edge = ktime_add_ns(edge, space);
delta = ktime_to_ns(ktime_sub(edge,
ktime_get()));
if (delta > 0)
ndelay(delta);
}
edge = last;
}
}
}
static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
unsigned int count)
{
struct gpio_ir *gpio_ir = dev->priv;
unsigned long flags;
local_irq_save(flags);
if (gpio_ir->carrier)
gpio_ir_tx_modulated(gpio_ir, txbuf, count);
else
gpio_ir_tx_unmodulated(gpio_ir, txbuf, count);
local_irq_restore(flags);
return count;
}
static int gpio_ir_tx_probe(struct platform_device *pdev)
{
struct gpio_ir *gpio_ir;
struct rc_dev *rcdev;
int rc;
gpio_ir = devm_kmalloc(&pdev->dev, sizeof(*gpio_ir), GFP_KERNEL);
if (!gpio_ir)
return -ENOMEM;
rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
if (!rcdev)
return -ENOMEM;
gpio_ir->gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
if (IS_ERR(gpio_ir->gpio)) {
if (PTR_ERR(gpio_ir->gpio) != -EPROBE_DEFER)
dev_err(&pdev->dev, "Failed to get gpio (%ld)\n",
PTR_ERR(gpio_ir->gpio));
return PTR_ERR(gpio_ir->gpio);
}
rcdev->priv = gpio_ir;
rcdev->driver_name = DRIVER_NAME;
rcdev->device_name = DEVICE_NAME;
rcdev->tx_ir = gpio_ir_tx;
rcdev->s_tx_duty_cycle = gpio_ir_tx_set_duty_cycle;
rcdev->s_tx_carrier = gpio_ir_tx_set_carrier;
gpio_ir->carrier = 38000;
gpio_ir->duty_cycle = 50;
rc = devm_rc_register_device(&pdev->dev, rcdev);
if (rc < 0)
dev_err(&pdev->dev, "failed to register rc device\n");
return rc;
}
static struct platform_driver gpio_ir_tx_driver = {
.probe = gpio_ir_tx_probe,
.driver = {
.name = DRIVER_NAME,
.of_match_table = of_match_ptr(gpio_ir_tx_of_match),
},
};
module_platform_driver(gpio_ir_tx_driver);
MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
MODULE_AUTHOR("Sean Young <sean@mess.org>");
MODULE_LICENSE("GPL");