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 <log.h>
12#include <malloc.h>
13#include <asm/global_data.h>
14#include <asm/gpio.h>
15#include <linux/delay.h>
16
17DECLARE_GLOBAL_DATA_PTR;
18
19struct i2c_arbitrator_priv {
20	struct gpio_desc ap_claim;
21	struct gpio_desc ec_claim;
22	uint slew_delay_us;
23	uint wait_retry_ms;
24	uint wait_free_ms;
25};
26
27int i2c_arbitrator_deselect(struct udevice *mux, struct udevice *bus,
28			    uint channel)
29{
30	struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
31	int ret;
32
33	debug("%s: %s\n", __func__, mux->name);
34	ret = dm_gpio_set_value(&priv->ap_claim, 0);
35	udelay(priv->slew_delay_us);
36
37	return ret;
38}
39
40int i2c_arbitrator_select(struct udevice *mux, struct udevice *bus,
41			  uint channel)
42{
43	struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
44	unsigned start;
45	int ret;
46
47	debug("%s: %s\n", __func__, mux->name);
48	/* Start a round of trying to claim the bus */
49	start = get_timer(0);
50	do {
51		unsigned start_retry;
52		int waiting = 0;
53
54		/* Indicate that we want to claim the bus */
55		ret = dm_gpio_set_value(&priv->ap_claim, 1);
56		if (ret)
57			goto err;
58		udelay(priv->slew_delay_us);
59
60		/* Wait for the EC to release it */
61		start_retry = get_timer(0);
62		while (get_timer(start_retry) < priv->wait_retry_ms) {
63			ret = dm_gpio_get_value(&priv->ec_claim);
64			if (ret < 0) {
65				goto err;
66			} else if (!ret) {
67				/* We got it, so return */
68				return 0;
69			}
70
71			if (!waiting)
72				waiting = 1;
73		}
74
75		/* It didn't release, so give up, wait, and try again */
76		ret = dm_gpio_set_value(&priv->ap_claim, 0);
77		if (ret)
78			goto err;
79
80		mdelay(priv->wait_retry_ms);
81	} while (get_timer(start) < priv->wait_free_ms);
82
83	/* Give up, release our claim */
84	printf("I2C: Could not claim bus, timeout %lu\n", get_timer(start));
85	ret = -ETIMEDOUT;
86	ret = 0;
87err:
88	return ret;
89}
90
91static int i2c_arbitrator_probe(struct udevice *dev)
92{
93	struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
94	const void *blob = gd->fdt_blob;
95	int node = dev_of_offset(dev);
96	int ret;
97
98	debug("%s: %s\n", __func__, dev->name);
99	priv->slew_delay_us = fdtdec_get_int(blob, node, "slew-delay-us", 0);
100	priv->wait_retry_ms = fdtdec_get_int(blob, node, "wait-retry-us", 0) /
101		1000;
102	priv->wait_free_ms = fdtdec_get_int(blob, node, "wait-free-us", 0) /
103		1000;
104	ret = gpio_request_by_name(dev, "our-claim-gpio", 0, &priv->ap_claim,
105				   GPIOD_IS_OUT);
106	if (ret)
107		goto err;
108	ret = gpio_request_by_name(dev, "their-claim-gpios", 0, &priv->ec_claim,
109				   GPIOD_IS_IN);
110	if (ret)
111		goto err_ec_gpio;
112
113	return 0;
114
115err_ec_gpio:
116	dm_gpio_free(dev, &priv->ap_claim);
117err:
118	debug("%s: ret=%d\n", __func__, ret);
119	return ret;
120}
121
122static int i2c_arbitrator_remove(struct udevice *dev)
123{
124	struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
125
126	dm_gpio_free(dev, &priv->ap_claim);
127	dm_gpio_free(dev, &priv->ec_claim);
128
129	return 0;
130}
131
132static const struct i2c_mux_ops i2c_arbitrator_ops = {
133	.select		= i2c_arbitrator_select,
134	.deselect	= i2c_arbitrator_deselect,
135};
136
137static const struct udevice_id i2c_arbitrator_ids[] = {
138	{ .compatible = "i2c-arb-gpio-challenge" },
139	{ }
140};
141
142U_BOOT_DRIVER(i2c_arbitrator) = {
143	.name = "i2c_arbitrator",
144	.id = UCLASS_I2C_MUX,
145	.of_match = i2c_arbitrator_ids,
146	.probe = i2c_arbitrator_probe,
147	.remove = i2c_arbitrator_remove,
148	.ops = &i2c_arbitrator_ops,
149	.priv_auto	= sizeof(struct i2c_arbitrator_priv),
150};
151