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

   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 };
  23
  24 static const struct of_device_id gpio_ir_tx_of_match[] = {
  25         { .compatible = "gpio-ir-tx", },
  26         { },
  27 };
  28 MODULE_DEVICE_TABLE(of, gpio_ir_tx_of_match);
  29
  30 static int gpio_ir_tx_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
  31 {
  32         struct gpio_ir *gpio_ir = dev->priv;
  33
  34         gpio_ir->duty_cycle = duty_cycle;
  35
  36         return 0;
  37 }
  38
  39 static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier)
  40 {
  41         struct gpio_ir *gpio_ir = dev->priv;
  42
  43         if (carrier > 500000)
  44                 return -EINVAL;
  45
  46         gpio_ir->carrier = carrier;
  47
  48         return 0;
  49 }
  50
  51 static void delay_until(ktime_t until)
  52 {
  53         /*
  54          * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
  55          * m68k ndelay(s64) does not compile; so use s32 rather than s64.
  56          */
  57         s32 delta;
  58
  59         while (true) {
  60                 delta = ktime_us_delta(until, ktime_get());
  61                 if (delta <= 0)
  62                         return;
  63
  64                 /* udelay more than 1ms may not work */
  65                 if (delta >= 1000) {
  66                         mdelay(delta / 1000);
  67                         continue;
  68                 }
  69
  70                 udelay(delta);
  71                 break;
  72         }
  73 }
  74
  75 static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
  76                                    uint count)
  77 {
  78         ktime_t edge;
  79         int i;
  80
  81         edge = ktime_get();
  82
  83         for (i = 0; i < count; i++) {
  84                 gpiod_set_value(gpio_ir->gpio, !(i % 2));
  85
  86                 edge = ktime_add_us(edge, txbuf[i]);
  87                 delay_until(edge);
  88         }
  89
  90         gpiod_set_value(gpio_ir->gpio, 0);
  91 }
  92
  93 static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
  94                                  uint count)
  95 {
  96         ktime_t edge;
  97         /*
  98          * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
  99          * m68k ndelay(s64) does not compile; so use s32 rather than s64.
 100          */
 101         s32 delta;
 102         int i;
 103         unsigned int pulse, space;
 104
 105         /* Ensure the dividend fits into 32 bit */
 106         pulse = DIV_ROUND_CLOSEST(gpio_ir->duty_cycle * (NSEC_PER_SEC / 100),
 107                                   gpio_ir->carrier);
 108         space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
 109                                   (NSEC_PER_SEC / 100), gpio_ir->carrier);
 110
 111         edge = ktime_get();
 112
 113         for (i = 0; i < count; i++) {
 114                 if (i % 2) {
 115                         // space
 116                         edge = ktime_add_us(edge, txbuf[i]);
 117                         delay_until(edge);
 118                 } else {
 119                         // pulse
 120                         ktime_t last = ktime_add_us(edge, txbuf[i]);
 121
 122                         while (ktime_before(ktime_get(), last)) {
 123                                 gpiod_set_value(gpio_ir->gpio, 1);
 124                                 edge = ktime_add_ns(edge, pulse);
 125                                 delta = ktime_to_ns(ktime_sub(edge,
 126                                                               ktime_get()));
 127                                 if (delta > 0)
 128                                         ndelay(delta);
 129                                 gpiod_set_value(gpio_ir->gpio, 0);
 130                                 edge = ktime_add_ns(edge, space);
 131                                 delta = ktime_to_ns(ktime_sub(edge,
 132                                                               ktime_get()));
 133                                 if (delta > 0)
 134                                         ndelay(delta);
 135                         }
 136
 137                         edge = last;
 138                 }
 139         }
 140 }
 141
 142 static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
 143                       unsigned int count)
 144 {
 145         struct gpio_ir *gpio_ir = dev->priv;
 146         unsigned long flags;
 147
 148         local_irq_save(flags);
 149         if (gpio_ir->carrier)
 150                 gpio_ir_tx_modulated(gpio_ir, txbuf, count);
 151         else
 152                 gpio_ir_tx_unmodulated(gpio_ir, txbuf, count);
 153         local_irq_restore(flags);
 154
 155         return count;
 156 }
 157
 158 static int gpio_ir_tx_probe(struct platform_device *pdev)
 159 {
 160         struct gpio_ir *gpio_ir;
 161         struct rc_dev *rcdev;
 162         int rc;
 163
 164         gpio_ir = devm_kmalloc(&pdev->dev, sizeof(*gpio_ir), GFP_KERNEL);
 165         if (!gpio_ir)
 166                 return -ENOMEM;
 167
 168         rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
 169         if (!rcdev)
 170                 return -ENOMEM;
 171
 172         gpio_ir->gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
 173         if (IS_ERR(gpio_ir->gpio))
 174                 return dev_err_probe(&pdev->dev, PTR_ERR(gpio_ir->gpio),
 175                                      "Failed to get gpio\n");
 176
 177         rcdev->priv = gpio_ir;
 178         rcdev->driver_name = DRIVER_NAME;
 179         rcdev->device_name = DEVICE_NAME;
 180         rcdev->tx_ir = gpio_ir_tx;
 181         rcdev->s_tx_duty_cycle = gpio_ir_tx_set_duty_cycle;
 182         rcdev->s_tx_carrier = gpio_ir_tx_set_carrier;
 183
 184         gpio_ir->carrier = 38000;
 185         gpio_ir->duty_cycle = 50;
 186
 187         rc = devm_rc_register_device(&pdev->dev, rcdev);
 188         if (rc < 0)
 189                 dev_err(&pdev->dev, "failed to register rc device\n");
 190
 191         return rc;
 192 }
 193
 194 static struct platform_driver gpio_ir_tx_driver = {
 195         .probe  = gpio_ir_tx_probe,
 196         .driver = {
 197                 .name   = DRIVER_NAME,
 198                 .of_match_table = gpio_ir_tx_of_match,
 199         },
 200 };
 201 module_platform_driver(gpio_ir_tx_driver);
 202
 203 MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
 204 MODULE_AUTHOR("Sean Young <sean@mess.org>");
 205 MODULE_LICENSE("GPL");