root/drivers/media/rc/gpio-ir-tx.c

DEFINITIONS

1. gpio_ir_tx_set_duty_cycle
2. gpio_ir_tx_set_carrier
3. gpio_ir_tx
4. gpio_ir_tx_probe

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2017 Sean Young <sean@mess.org>
   4  */
   5 
   6 #include <linux/kernel.h>
   7 #include <linux/module.h>
   8 #include <linux/gpio/consumer.h>
   9 #include <linux/delay.h>
  10 #include <linux/slab.h>
  11 #include <linux/of.h>
  12 #include <linux/platform_device.h>
  13 #include <media/rc-core.h>
  14 
  15 #define DRIVER_NAME     "gpio-ir-tx"
  16 #define DEVICE_NAME     "GPIO IR Bit Banging Transmitter"
  17 
  18 struct gpio_ir {
  19         struct gpio_desc *gpio;
  20         unsigned int carrier;
  21         unsigned int duty_cycle;
  22         /* we need a spinlock to hold the cpu while transmitting */
  23         spinlock_t lock;
  24 };
  25 
  26 static const struct of_device_id gpio_ir_tx_of_match[] = {
  27         { .compatible = "gpio-ir-tx", },
  28         { },
  29 };
  30 MODULE_DEVICE_TABLE(of, gpio_ir_tx_of_match);
  31 
  32 static int gpio_ir_tx_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
  33 {
  34         struct gpio_ir *gpio_ir = dev->priv;
  35 
  36         gpio_ir->duty_cycle = duty_cycle;
  37 
  38         return 0;
  39 }
  40 
  41 static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier)
  42 {
  43         struct gpio_ir *gpio_ir = dev->priv;
  44 
  45         if (!carrier)
  46                 return -EINVAL;
  47 
  48         gpio_ir->carrier = carrier;
  49 
  50         return 0;
  51 }
  52 
  53 static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
  54                       unsigned int count)
  55 {
  56         struct gpio_ir *gpio_ir = dev->priv;
  57         unsigned long flags;
  58         ktime_t edge;
  59         /*
  60          * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
  61          * m68k ndelay(s64) does not compile; so use s32 rather than s64.
  62          */
  63         s32 delta;
  64         int i;
  65         unsigned int pulse, space;
  66 
  67         /* Ensure the dividend fits into 32 bit */
  68         pulse = DIV_ROUND_CLOSEST(gpio_ir->duty_cycle * (NSEC_PER_SEC / 100),
  69                                   gpio_ir->carrier);
  70         space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
  71                                   (NSEC_PER_SEC / 100), gpio_ir->carrier);
  72 
  73         spin_lock_irqsave(&gpio_ir->lock, flags);
  74 
  75         edge = ktime_get();
  76 
  77         for (i = 0; i < count; i++) {
  78                 if (i % 2) {
  79                         // space
  80                         edge = ktime_add_us(edge, txbuf[i]);
  81                         delta = ktime_us_delta(edge, ktime_get());
  82                         if (delta > 10) {
  83                                 spin_unlock_irqrestore(&gpio_ir->lock, flags);
  84                                 usleep_range(delta, delta + 10);
  85                                 spin_lock_irqsave(&gpio_ir->lock, flags);
  86                         } else if (delta > 0) {
  87                                 udelay(delta);
  88                         }
  89                 } else {
  90                         // pulse
  91                         ktime_t last = ktime_add_us(edge, txbuf[i]);
  92 
  93                         while (ktime_before(ktime_get(), last)) {
  94                                 gpiod_set_value(gpio_ir->gpio, 1);
  95                                 edge = ktime_add_ns(edge, pulse);
  96                                 delta = ktime_to_ns(ktime_sub(edge,
  97                                                               ktime_get()));
  98                                 if (delta > 0)
  99                                         ndelay(delta);
 100                                 gpiod_set_value(gpio_ir->gpio, 0);
 101                                 edge = ktime_add_ns(edge, space);
 102                                 delta = ktime_to_ns(ktime_sub(edge,
 103                                                               ktime_get()));
 104                                 if (delta > 0)
 105                                         ndelay(delta);
 106                         }
 107 
 108                         edge = last;
 109                 }
 110         }
 111 
 112         spin_unlock_irqrestore(&gpio_ir->lock, flags);
 113 
 114         return count;
 115 }
 116 
 117 static int gpio_ir_tx_probe(struct platform_device *pdev)
 118 {
 119         struct gpio_ir *gpio_ir;
 120         struct rc_dev *rcdev;
 121         int rc;
 122 
 123         gpio_ir = devm_kmalloc(&pdev->dev, sizeof(*gpio_ir), GFP_KERNEL);
 124         if (!gpio_ir)
 125                 return -ENOMEM;
 126 
 127         rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
 128         if (!rcdev)
 129                 return -ENOMEM;
 130 
 131         gpio_ir->gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
 132         if (IS_ERR(gpio_ir->gpio)) {
 133                 if (PTR_ERR(gpio_ir->gpio) != -EPROBE_DEFER)
 134                         dev_err(&pdev->dev, "Failed to get gpio (%ld)\n",
 135                                 PTR_ERR(gpio_ir->gpio));
 136                 return PTR_ERR(gpio_ir->gpio);
 137         }
 138 
 139         rcdev->priv = gpio_ir;
 140         rcdev->driver_name = DRIVER_NAME;
 141         rcdev->device_name = DEVICE_NAME;
 142         rcdev->tx_ir = gpio_ir_tx;
 143         rcdev->s_tx_duty_cycle = gpio_ir_tx_set_duty_cycle;
 144         rcdev->s_tx_carrier = gpio_ir_tx_set_carrier;
 145 
 146         gpio_ir->carrier = 38000;
 147         gpio_ir->duty_cycle = 50;
 148         spin_lock_init(&gpio_ir->lock);
 149 
 150         rc = devm_rc_register_device(&pdev->dev, rcdev);
 151         if (rc < 0)
 152                 dev_err(&pdev->dev, "failed to register rc device\n");
 153 
 154         return rc;
 155 }
 156 
 157 static struct platform_driver gpio_ir_tx_driver = {
 158         .probe  = gpio_ir_tx_probe,
 159         .driver = {
 160                 .name   = DRIVER_NAME,
 161                 .of_match_table = of_match_ptr(gpio_ir_tx_of_match),
 162         },
 163 };
 164 module_platform_driver(gpio_ir_tx_driver);
 165 
 166 MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
 167 MODULE_AUTHOR("Sean Young <sean@mess.org>");
 168 MODULE_LICENSE("GPL");