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 8 #include <common.h> 9 #include <dm.h> 10 #include <errno.h> 11 #include <i2c.h> 12 #include <asm/gpio.h> 13 14 DECLARE_GLOBAL_DATA_PTR; 15 16 struct i2c_arbitrator_priv { 17 struct gpio_desc ap_claim; 18 struct gpio_desc ec_claim; 19 uint slew_delay_us; 20 uint wait_retry_ms; 21 uint wait_free_ms; 22 }; 23 24 int i2c_arbitrator_deselect(struct udevice *mux, struct udevice *bus, 25 uint channel) 26 { 27 struct i2c_arbitrator_priv *priv = dev_get_priv(mux); 28 int ret; 29 30 debug("%s: %s\n", __func__, mux->name); 31 ret = dm_gpio_set_value(&priv->ap_claim, 0); 32 udelay(priv->slew_delay_us); 33 34 return ret; 35 } 36 37 int i2c_arbitrator_select(struct udevice *mux, struct udevice *bus, 38 uint channel) 39 { 40 struct i2c_arbitrator_priv *priv = dev_get_priv(mux); 41 unsigned start; 42 int ret; 43 44 debug("%s: %s\n", __func__, mux->name); 45 /* Start a round of trying to claim the bus */ 46 start = get_timer(0); 47 do { 48 unsigned start_retry; 49 int waiting = 0; 50 51 /* Indicate that we want to claim the bus */ 52 ret = dm_gpio_set_value(&priv->ap_claim, 1); 53 if (ret) 54 goto err; 55 udelay(priv->slew_delay_us); 56 57 /* Wait for the EC to release it */ 58 start_retry = get_timer(0); 59 while (get_timer(start_retry) < priv->wait_retry_ms) { 60 ret = dm_gpio_get_value(&priv->ec_claim); 61 if (ret < 0) { 62 goto err; 63 } else if (!ret) { 64 /* We got it, so return */ 65 return 0; 66 } 67 68 if (!waiting) 69 waiting = 1; 70 } 71 72 /* It didn't release, so give up, wait, and try again */ 73 ret = dm_gpio_set_value(&priv->ap_claim, 0); 74 if (ret) 75 goto err; 76 77 mdelay(priv->wait_retry_ms); 78 } while (get_timer(start) < priv->wait_free_ms); 79 80 /* Give up, release our claim */ 81 printf("I2C: Could not claim bus, timeout %lu\n", get_timer(start)); 82 ret = -ETIMEDOUT; 83 ret = 0; 84 err: 85 return ret; 86 } 87 88 static int i2c_arbitrator_probe(struct udevice *dev) 89 { 90 struct i2c_arbitrator_priv *priv = dev_get_priv(dev); 91 const void *blob = gd->fdt_blob; 92 int node = dev->of_offset; 93 int ret; 94 95 debug("%s: %s\n", __func__, dev->name); 96 priv->slew_delay_us = fdtdec_get_int(blob, node, "slew-delay-us", 0); 97 priv->wait_retry_ms = fdtdec_get_int(blob, node, "wait-retry-us", 0) / 98 1000; 99 priv->wait_free_ms = fdtdec_get_int(blob, node, "wait-free-us", 0) / 100 1000; 101 ret = gpio_request_by_name(dev, "our-claim-gpio", 0, &priv->ap_claim, 102 GPIOD_IS_OUT); 103 if (ret) 104 goto err; 105 ret = gpio_request_by_name(dev, "their-claim-gpios", 0, &priv->ec_claim, 106 GPIOD_IS_IN); 107 if (ret) 108 goto err_ec_gpio; 109 110 return 0; 111 112 err_ec_gpio: 113 dm_gpio_free(dev, &priv->ap_claim); 114 err: 115 debug("%s: ret=%d\n", __func__, ret); 116 return ret; 117 } 118 119 static int i2c_arbitrator_remove(struct udevice *dev) 120 { 121 struct i2c_arbitrator_priv *priv = dev_get_priv(dev); 122 123 dm_gpio_free(dev, &priv->ap_claim); 124 dm_gpio_free(dev, &priv->ec_claim); 125 126 return 0; 127 } 128 129 static const struct i2c_mux_ops i2c_arbitrator_ops = { 130 .select = i2c_arbitrator_select, 131 .deselect = i2c_arbitrator_deselect, 132 }; 133 134 static const struct udevice_id i2c_arbitrator_ids[] = { 135 { .compatible = "i2c-arb-gpio-challenge" }, 136 { } 137 }; 138 139 U_BOOT_DRIVER(i2c_arbitrator) = { 140 .name = "i2c_arbitrator", 141 .id = UCLASS_I2C_MUX, 142 .of_match = i2c_arbitrator_ids, 143 .probe = i2c_arbitrator_probe, 144 .remove = i2c_arbitrator_remove, 145 .ops = &i2c_arbitrator_ops, 146 .priv_auto_alloc_size = sizeof(struct i2c_arbitrator_priv), 147 }; 148