1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Copyright (c) 2015 Google, Inc
4  * Written by Simon Glass <sjg@chromium.org>
5  */
6 
7 #include <common.h>
8 #include <dm.h>
9 #include <errno.h>
10 #include <i2c.h>
11 #include <asm/gpio.h>
12 
13 DECLARE_GLOBAL_DATA_PTR;
14 
15 struct i2c_arbitrator_priv {
16 	struct gpio_desc ap_claim;
17 	struct gpio_desc ec_claim;
18 	uint slew_delay_us;
19 	uint wait_retry_ms;
20 	uint wait_free_ms;
21 };
22 
23 int i2c_arbitrator_deselect(struct udevice *mux, struct udevice *bus,
24 			    uint channel)
25 {
26 	struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
27 	int ret;
28 
29 	debug("%s: %s\n", __func__, mux->name);
30 	ret = dm_gpio_set_value(&priv->ap_claim, 0);
31 	udelay(priv->slew_delay_us);
32 
33 	return ret;
34 }
35 
36 int i2c_arbitrator_select(struct udevice *mux, struct udevice *bus,
37 			  uint channel)
38 {
39 	struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
40 	unsigned start;
41 	int ret;
42 
43 	debug("%s: %s\n", __func__, mux->name);
44 	/* Start a round of trying to claim the bus */
45 	start = get_timer(0);
46 	do {
47 		unsigned start_retry;
48 		int waiting = 0;
49 
50 		/* Indicate that we want to claim the bus */
51 		ret = dm_gpio_set_value(&priv->ap_claim, 1);
52 		if (ret)
53 			goto err;
54 		udelay(priv->slew_delay_us);
55 
56 		/* Wait for the EC to release it */
57 		start_retry = get_timer(0);
58 		while (get_timer(start_retry) < priv->wait_retry_ms) {
59 			ret = dm_gpio_get_value(&priv->ec_claim);
60 			if (ret < 0) {
61 				goto err;
62 			} else if (!ret) {
63 				/* We got it, so return */
64 				return 0;
65 			}
66 
67 			if (!waiting)
68 				waiting = 1;
69 		}
70 
71 		/* It didn't release, so give up, wait, and try again */
72 		ret = dm_gpio_set_value(&priv->ap_claim, 0);
73 		if (ret)
74 			goto err;
75 
76 		mdelay(priv->wait_retry_ms);
77 	} while (get_timer(start) < priv->wait_free_ms);
78 
79 	/* Give up, release our claim */
80 	printf("I2C: Could not claim bus, timeout %lu\n", get_timer(start));
81 	ret = -ETIMEDOUT;
82 	ret = 0;
83 err:
84 	return ret;
85 }
86 
87 static int i2c_arbitrator_probe(struct udevice *dev)
88 {
89 	struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
90 	const void *blob = gd->fdt_blob;
91 	int node = dev_of_offset(dev);
92 	int ret;
93 
94 	debug("%s: %s\n", __func__, dev->name);
95 	priv->slew_delay_us = fdtdec_get_int(blob, node, "slew-delay-us", 0);
96 	priv->wait_retry_ms = fdtdec_get_int(blob, node, "wait-retry-us", 0) /
97 		1000;
98 	priv->wait_free_ms = fdtdec_get_int(blob, node, "wait-free-us", 0) /
99 		1000;
100 	ret = gpio_request_by_name(dev, "our-claim-gpio", 0, &priv->ap_claim,
101 				   GPIOD_IS_OUT);
102 	if (ret)
103 		goto err;
104 	ret = gpio_request_by_name(dev, "their-claim-gpios", 0, &priv->ec_claim,
105 				   GPIOD_IS_IN);
106 	if (ret)
107 		goto err_ec_gpio;
108 
109 	return 0;
110 
111 err_ec_gpio:
112 	dm_gpio_free(dev, &priv->ap_claim);
113 err:
114 	debug("%s: ret=%d\n", __func__, ret);
115 	return ret;
116 }
117 
118 static int i2c_arbitrator_remove(struct udevice *dev)
119 {
120 	struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
121 
122 	dm_gpio_free(dev, &priv->ap_claim);
123 	dm_gpio_free(dev, &priv->ec_claim);
124 
125 	return 0;
126 }
127 
128 static const struct i2c_mux_ops i2c_arbitrator_ops = {
129 	.select		= i2c_arbitrator_select,
130 	.deselect	= i2c_arbitrator_deselect,
131 };
132 
133 static const struct udevice_id i2c_arbitrator_ids[] = {
134 	{ .compatible = "i2c-arb-gpio-challenge" },
135 	{ }
136 };
137 
138 U_BOOT_DRIVER(i2c_arbitrator) = {
139 	.name = "i2c_arbitrator",
140 	.id = UCLASS_I2C_MUX,
141 	.of_match = i2c_arbitrator_ids,
142 	.probe = i2c_arbitrator_probe,
143 	.remove = i2c_arbitrator_remove,
144 	.ops = &i2c_arbitrator_ops,
145 	.priv_auto_alloc_size = sizeof(struct i2c_arbitrator_priv),
146 };
147