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

   1 /*
   2  * Copyright (C) 2017 Sean Young <sean@mess.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/gpio/consumer.h>
  17 #include <linux/delay.h>
  18 #include <linux/slab.h>
  19 #include <linux/of.h>
  20 #include <linux/platform_device.h>
  21 #include <media/rc-core.h>
  22
  23 #define DRIVER_NAME     "gpio-ir-tx"
  24 #define DEVICE_NAME     "GPIO IR Bit Banging Transmitter"
  25
  26 struct gpio_ir {
  27         struct gpio_desc *gpio;
  28         unsigned int carrier;
  29         unsigned int duty_cycle;
  30         /* we need a spinlock to hold the cpu while transmitting */
  31         spinlock_t lock;
  32 };
  33
  34 static const struct of_device_id gpio_ir_tx_of_match[] = {
  35         { .compatible = "gpio-ir-tx", },
  36         { },
  37 };
  38 MODULE_DEVICE_TABLE(of, gpio_ir_tx_of_match);
  39
  40 static int gpio_ir_tx_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
  41 {
  42         struct gpio_ir *gpio_ir = dev->priv;
  43
  44         gpio_ir->duty_cycle = duty_cycle;
  45
  46         return 0;
  47 }
  48
  49 static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier)
  50 {
  51         struct gpio_ir *gpio_ir = dev->priv;
  52
  53         if (!carrier)
  54                 return -EINVAL;
  55
  56         gpio_ir->carrier = carrier;
  57
  58         return 0;
  59 }
  60
  61 static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
  62                       unsigned int count)
  63 {
  64         struct gpio_ir *gpio_ir = dev->priv;
  65         unsigned long flags;
  66         ktime_t edge;
  67         /*
  68          * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
  69          * m68k ndelay(s64) does not compile; so use s32 rather than s64.
  70          */
  71         s32 delta;
  72         int i;
  73         unsigned int pulse, space;
  74
  75         /* Ensure the dividend fits into 32 bit */
  76         pulse = DIV_ROUND_CLOSEST(gpio_ir->duty_cycle * (NSEC_PER_SEC / 100),
  77                                   gpio_ir->carrier);
  78         space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
  79                                   (NSEC_PER_SEC / 100), gpio_ir->carrier);
  80
  81         spin_lock_irqsave(&gpio_ir->lock, flags);
  82
  83         edge = ktime_get();
  84
  85         for (i = 0; i < count; i++) {
  86                 if (i % 2) {
  87                         // space
  88                         edge = ktime_add_us(edge, txbuf[i]);
  89                         delta = ktime_us_delta(edge, ktime_get());
  90                         if (delta > 10) {
  91                                 spin_unlock_irqrestore(&gpio_ir->lock, flags);
  92                                 usleep_range(delta, delta + 10);
  93                                 spin_lock_irqsave(&gpio_ir->lock, flags);
  94                         } else if (delta > 0) {
  95                                 udelay(delta);
  96                         }
  97                 } else {
  98                         // pulse
  99                         ktime_t last = ktime_add_us(edge, txbuf[i]);
 100
 101                         while (ktime_before(ktime_get(), last)) {
 102                                 gpiod_set_value(gpio_ir->gpio, 1);
 103                                 edge = ktime_add_ns(edge, pulse);
 104                                 delta = ktime_to_ns(ktime_sub(edge,
 105                                                               ktime_get()));
 106                                 if (delta > 0)
 107                                         ndelay(delta);
 108                                 gpiod_set_value(gpio_ir->gpio, 0);
 109                                 edge = ktime_add_ns(edge, space);
 110                                 delta = ktime_to_ns(ktime_sub(edge,
 111                                                               ktime_get()));
 112                                 if (delta > 0)
 113                                         ndelay(delta);
 114                         }
 115
 116                         edge = last;
 117                 }
 118         }
 119
 120         spin_unlock_irqrestore(&gpio_ir->lock, flags);
 121
 122         return count;
 123 }
 124
 125 static int gpio_ir_tx_probe(struct platform_device *pdev)
 126 {
 127         struct gpio_ir *gpio_ir;
 128         struct rc_dev *rcdev;
 129         int rc;
 130
 131         gpio_ir = devm_kmalloc(&pdev->dev, sizeof(*gpio_ir), GFP_KERNEL);
 132         if (!gpio_ir)
 133                 return -ENOMEM;
 134
 135         rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
 136         if (!rcdev)
 137                 return -ENOMEM;
 138
 139         gpio_ir->gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
 140         if (IS_ERR(gpio_ir->gpio)) {
 141                 if (PTR_ERR(gpio_ir->gpio) != -EPROBE_DEFER)
 142                         dev_err(&pdev->dev, "Failed to get gpio (%ld)\n",
 143                                 PTR_ERR(gpio_ir->gpio));
 144                 return PTR_ERR(gpio_ir->gpio);
 145         }
 146
 147         rcdev->priv = gpio_ir;
 148         rcdev->driver_name = DRIVER_NAME;
 149         rcdev->device_name = DEVICE_NAME;
 150         rcdev->tx_ir = gpio_ir_tx;
 151         rcdev->s_tx_duty_cycle = gpio_ir_tx_set_duty_cycle;
 152         rcdev->s_tx_carrier = gpio_ir_tx_set_carrier;
 153
 154         gpio_ir->carrier = 38000;
 155         gpio_ir->duty_cycle = 50;
 156         spin_lock_init(&gpio_ir->lock);
 157
 158         rc = devm_rc_register_device(&pdev->dev, rcdev);
 159         if (rc < 0)
 160                 dev_err(&pdev->dev, "failed to register rc device\n");
 161
 162         return rc;
 163 }
 164
 165 static struct platform_driver gpio_ir_tx_driver = {
 166         .probe  = gpio_ir_tx_probe,
 167         .driver = {
 168                 .name   = DRIVER_NAME,
 169                 .of_match_table = of_match_ptr(gpio_ir_tx_of_match),
 170         },
 171 };
 172 module_platform_driver(gpio_ir_tx_driver);
 173
 174 MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
 175 MODULE_AUTHOR("Sean Young <sean@mess.org>");
 176 MODULE_LICENSE("GPL");