i2c-arb-gpio-challenge.c 3.3 KB

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  1. /*
  2. * Copyright (c) 2015 Google, Inc
  3. * Written by Simon Glass <sjg@chromium.org>
  4. *
  5. * SPDX-License-Identifier: GPL-2.0+
  6. */
  7. #include <common.h>
  8. #include <dm.h>
  9. #include <errno.h>
  10. #include <i2c.h>
  11. #include <asm/gpio.h>
  12. DECLARE_GLOBAL_DATA_PTR;
  13. struct i2c_arbitrator_priv {
  14. struct gpio_desc ap_claim;
  15. struct gpio_desc ec_claim;
  16. uint slew_delay_us;
  17. uint wait_retry_ms;
  18. uint wait_free_ms;
  19. };
  20. int i2c_arbitrator_deselect(struct udevice *mux, struct udevice *bus,
  21. uint channel)
  22. {
  23. struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
  24. int ret;
  25. debug("%s: %s\n", __func__, mux->name);
  26. ret = dm_gpio_set_value(&priv->ap_claim, 0);
  27. udelay(priv->slew_delay_us);
  28. return ret;
  29. }
  30. int i2c_arbitrator_select(struct udevice *mux, struct udevice *bus,
  31. uint channel)
  32. {
  33. struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
  34. unsigned start;
  35. int ret;
  36. debug("%s: %s\n", __func__, mux->name);
  37. /* Start a round of trying to claim the bus */
  38. start = get_timer(0);
  39. do {
  40. unsigned start_retry;
  41. int waiting = 0;
  42. /* Indicate that we want to claim the bus */
  43. ret = dm_gpio_set_value(&priv->ap_claim, 1);
  44. if (ret)
  45. goto err;
  46. udelay(priv->slew_delay_us);
  47. /* Wait for the EC to release it */
  48. start_retry = get_timer(0);
  49. while (get_timer(start_retry) < priv->wait_retry_ms) {
  50. ret = dm_gpio_get_value(&priv->ec_claim);
  51. if (ret < 0) {
  52. goto err;
  53. } else if (!ret) {
  54. /* We got it, so return */
  55. return 0;
  56. }
  57. if (!waiting)
  58. waiting = 1;
  59. }
  60. /* It didn't release, so give up, wait, and try again */
  61. ret = dm_gpio_set_value(&priv->ap_claim, 0);
  62. if (ret)
  63. goto err;
  64. mdelay(priv->wait_retry_ms);
  65. } while (get_timer(start) < priv->wait_free_ms);
  66. /* Give up, release our claim */
  67. printf("I2C: Could not claim bus, timeout %lu\n", get_timer(start));
  68. ret = -ETIMEDOUT;
  69. ret = 0;
  70. err:
  71. return ret;
  72. }
  73. static int i2c_arbitrator_probe(struct udevice *dev)
  74. {
  75. struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
  76. const void *blob = gd->fdt_blob;
  77. int node = dev->of_offset;
  78. int ret;
  79. debug("%s: %s\n", __func__, dev->name);
  80. priv->slew_delay_us = fdtdec_get_int(blob, node, "slew-delay-us", 0);
  81. priv->wait_retry_ms = fdtdec_get_int(blob, node, "wait-retry-us", 0) /
  82. 1000;
  83. priv->wait_free_ms = fdtdec_get_int(blob, node, "wait-free-us", 0) /
  84. 1000;
  85. ret = gpio_request_by_name(dev, "our-claim-gpio", 0, &priv->ap_claim,
  86. GPIOD_IS_OUT);
  87. if (ret)
  88. goto err;
  89. ret = gpio_request_by_name(dev, "their-claim-gpios", 0, &priv->ec_claim,
  90. GPIOD_IS_IN);
  91. if (ret)
  92. goto err_ec_gpio;
  93. return 0;
  94. err_ec_gpio:
  95. dm_gpio_free(dev, &priv->ap_claim);
  96. err:
  97. debug("%s: ret=%d\n", __func__, ret);
  98. return ret;
  99. }
  100. static int i2c_arbitrator_remove(struct udevice *dev)
  101. {
  102. struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
  103. dm_gpio_free(dev, &priv->ap_claim);
  104. dm_gpio_free(dev, &priv->ec_claim);
  105. return 0;
  106. }
  107. static const struct i2c_mux_ops i2c_arbitrator_ops = {
  108. .select = i2c_arbitrator_select,
  109. .deselect = i2c_arbitrator_deselect,
  110. };
  111. static const struct udevice_id i2c_arbitrator_ids[] = {
  112. { .compatible = "i2c-arb-gpio-challenge" },
  113. { }
  114. };
  115. U_BOOT_DRIVER(i2c_arbitrator) = {
  116. .name = "i2c_arbitrator",
  117. .id = UCLASS_I2C_MUX,
  118. .of_match = i2c_arbitrator_ids,
  119. .probe = i2c_arbitrator_probe,
  120. .remove = i2c_arbitrator_remove,
  121. .ops = &i2c_arbitrator_ops,
  122. .priv_auto_alloc_size = sizeof(struct i2c_arbitrator_priv),
  123. };