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(dev);
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