gpio-ir-tx.c 4.5 KB

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  1. // SPDX-License-Identifier: GPL-2.0-or-later
  2. /*
  3. * Copyright (C) 2017 Sean Young <sean@mess.org>
  4. */
  5. #include <linux/kernel.h>
  6. #include <linux/module.h>
  7. #include <linux/gpio/consumer.h>
  8. #include <linux/delay.h>
  9. #include <linux/slab.h>
  10. #include <linux/of.h>
  11. #include <linux/platform_device.h>
  12. #include <media/rc-core.h>
  13. #define DRIVER_NAME "gpio-ir-tx"
  14. #define DEVICE_NAME "GPIO IR Bit Banging Transmitter"
  15. struct gpio_ir {
  16. struct gpio_desc *gpio;
  17. unsigned int carrier;
  18. unsigned int duty_cycle;
  19. };
  20. static const struct of_device_id gpio_ir_tx_of_match[] = {
  21. { .compatible = "gpio-ir-tx", },
  22. { },
  23. };
  24. MODULE_DEVICE_TABLE(of, gpio_ir_tx_of_match);
  25. static int gpio_ir_tx_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
  26. {
  27. struct gpio_ir *gpio_ir = dev->priv;
  28. gpio_ir->duty_cycle = duty_cycle;
  29. return 0;
  30. }
  31. static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier)
  32. {
  33. struct gpio_ir *gpio_ir = dev->priv;
  34. if (carrier > 500000)
  35. return -EINVAL;
  36. gpio_ir->carrier = carrier;
  37. return 0;
  38. }
  39. static void delay_until(ktime_t until)
  40. {
  41. /*
  42. * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
  43. * m68k ndelay(s64) does not compile; so use s32 rather than s64.
  44. */
  45. s32 delta;
  46. while (true) {
  47. delta = ktime_us_delta(until, ktime_get());
  48. if (delta <= 0)
  49. return;
  50. /* udelay more than 1ms may not work */
  51. delta = min(delta, 1000);
  52. udelay(delta);
  53. }
  54. }
  55. static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
  56. uint count)
  57. {
  58. ktime_t edge;
  59. int i;
  60. local_irq_disable();
  61. edge = ktime_get();
  62. for (i = 0; i < count; i++) {
  63. gpiod_set_value(gpio_ir->gpio, !(i % 2));
  64. edge = ktime_add_us(edge, txbuf[i]);
  65. delay_until(edge);
  66. }
  67. gpiod_set_value(gpio_ir->gpio, 0);
  68. }
  69. static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
  70. uint count)
  71. {
  72. ktime_t edge;
  73. /*
  74. * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
  75. * m68k ndelay(s64) does not compile; so use s32 rather than s64.
  76. */
  77. s32 delta;
  78. int i;
  79. unsigned int pulse, space;
  80. /* Ensure the dividend fits into 32 bit */
  81. pulse = DIV_ROUND_CLOSEST(gpio_ir->duty_cycle * (NSEC_PER_SEC / 100),
  82. gpio_ir->carrier);
  83. space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
  84. (NSEC_PER_SEC / 100), gpio_ir->carrier);
  85. local_irq_disable();
  86. edge = ktime_get();
  87. for (i = 0; i < count; i++) {
  88. if (i % 2) {
  89. // space
  90. edge = ktime_add_us(edge, txbuf[i]);
  91. delay_until(edge);
  92. } else {
  93. // pulse
  94. ktime_t last = ktime_add_us(edge, txbuf[i]);
  95. while (ktime_before(ktime_get(), last)) {
  96. gpiod_set_value(gpio_ir->gpio, 1);
  97. edge = ktime_add_ns(edge, pulse);
  98. delta = ktime_to_ns(ktime_sub(edge,
  99. ktime_get()));
  100. if (delta > 0)
  101. ndelay(delta);
  102. gpiod_set_value(gpio_ir->gpio, 0);
  103. edge = ktime_add_ns(edge, space);
  104. delta = ktime_to_ns(ktime_sub(edge,
  105. ktime_get()));
  106. if (delta > 0)
  107. ndelay(delta);
  108. }
  109. edge = last;
  110. }
  111. }
  112. }
  113. static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
  114. unsigned int count)
  115. {
  116. struct gpio_ir *gpio_ir = dev->priv;
  117. unsigned long flags;
  118. local_irq_save(flags);
  119. if (gpio_ir->carrier)
  120. gpio_ir_tx_modulated(gpio_ir, txbuf, count);
  121. else
  122. gpio_ir_tx_unmodulated(gpio_ir, txbuf, count);
  123. local_irq_restore(flags);
  124. return count;
  125. }
  126. static int gpio_ir_tx_probe(struct platform_device *pdev)
  127. {
  128. struct gpio_ir *gpio_ir;
  129. struct rc_dev *rcdev;
  130. int rc;
  131. gpio_ir = devm_kmalloc(&pdev->dev, sizeof(*gpio_ir), GFP_KERNEL);
  132. if (!gpio_ir)
  133. return -ENOMEM;
  134. rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
  135. if (!rcdev)
  136. return -ENOMEM;
  137. gpio_ir->gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
  138. if (IS_ERR(gpio_ir->gpio)) {
  139. if (PTR_ERR(gpio_ir->gpio) != -EPROBE_DEFER)
  140. dev_err(&pdev->dev, "Failed to get gpio (%ld)\n",
  141. PTR_ERR(gpio_ir->gpio));
  142. return PTR_ERR(gpio_ir->gpio);
  143. }
  144. rcdev->priv = gpio_ir;
  145. rcdev->driver_name = DRIVER_NAME;
  146. rcdev->device_name = DEVICE_NAME;
  147. rcdev->tx_ir = gpio_ir_tx;
  148. rcdev->s_tx_duty_cycle = gpio_ir_tx_set_duty_cycle;
  149. rcdev->s_tx_carrier = gpio_ir_tx_set_carrier;
  150. gpio_ir->carrier = 38000;
  151. gpio_ir->duty_cycle = 50;
  152. rc = devm_rc_register_device(&pdev->dev, rcdev);
  153. if (rc < 0)
  154. dev_err(&pdev->dev, "failed to register rc device\n");
  155. return rc;
  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. MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
  166. MODULE_AUTHOR("Sean Young <sean@mess.org>");
  167. MODULE_LICENSE("GPL");