1/*
2 * Intel BayTrail PMIC I2C bus semaphore implementaion
3 * Copyright (c) 2014, Intel Corporation.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
12 * more details.
13 */
14#include <linux/module.h>
15#include <linux/delay.h>
16#include <linux/device.h>
17#include <linux/acpi.h>
18#include <linux/i2c.h>
19#include <linux/interrupt.h>
20
21#include <asm/iosf_mbi.h>
22
23#include "i2c-designware-core.h"
24
25#define SEMAPHORE_TIMEOUT	100
26#define PUNIT_SEMAPHORE		0x7
27#define PUNIT_SEMAPHORE_BIT	BIT(0)
28#define PUNIT_SEMAPHORE_ACQUIRE	BIT(1)
29
30static unsigned long acquired;
31
32static int get_sem(struct device *dev, u32 *sem)
33{
34	u32 data;
35	int ret;
36
37	ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, PUNIT_SEMAPHORE,
38				&data);
39	if (ret) {
40		dev_err(dev, "iosf failed to read punit semaphore\n");
41		return ret;
42	}
43
44	*sem = data & PUNIT_SEMAPHORE_BIT;
45
46	return 0;
47}
48
49static void reset_semaphore(struct device *dev)
50{
51	u32 data;
52
53	if (iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,
54				PUNIT_SEMAPHORE, &data)) {
55		dev_err(dev, "iosf failed to reset punit semaphore during read\n");
56		return;
57	}
58
59	data &= ~PUNIT_SEMAPHORE_BIT;
60	if (iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE,
61				PUNIT_SEMAPHORE, data))
62		dev_err(dev, "iosf failed to reset punit semaphore during write\n");
63}
64
65static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
66{
67	u32 sem;
68	int ret;
69	unsigned long start, end;
70
71	might_sleep();
72
73	if (!dev || !dev->dev)
74		return -ENODEV;
75
76	if (!dev->release_lock)
77		return 0;
78
79	/* host driver writes to side band semaphore register */
80	ret = iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE,
81				PUNIT_SEMAPHORE, PUNIT_SEMAPHORE_ACQUIRE);
82	if (ret) {
83		dev_err(dev->dev, "iosf punit semaphore request failed\n");
84		return ret;
85	}
86
87	/* host driver waits for bit 0 to be set in semaphore register */
88	start = jiffies;
89	end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
90	do {
91		ret = get_sem(dev->dev, &sem);
92		if (!ret && sem) {
93			acquired = jiffies;
94			dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
95				jiffies_to_msecs(jiffies - start));
96			return 0;
97		}
98
99		usleep_range(1000, 2000);
100	} while (time_before(jiffies, end));
101
102	dev_err(dev->dev, "punit semaphore timed out, resetting\n");
103	reset_semaphore(dev->dev);
104
105	ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,
106				PUNIT_SEMAPHORE, &sem);
107	if (ret)
108		dev_err(dev->dev, "iosf failed to read punit semaphore\n");
109	else
110		dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
111
112	WARN_ON(1);
113
114	return -ETIMEDOUT;
115}
116
117static void baytrail_i2c_release(struct dw_i2c_dev *dev)
118{
119	if (!dev || !dev->dev)
120		return;
121
122	if (!dev->acquire_lock)
123		return;
124
125	reset_semaphore(dev->dev);
126	dev_dbg(dev->dev, "punit semaphore held for %ums\n",
127		jiffies_to_msecs(jiffies - acquired));
128}
129
130int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev)
131{
132	acpi_status status;
133	unsigned long long shared_host = 0;
134	acpi_handle handle;
135
136	if (!dev || !dev->dev)
137		return 0;
138
139	handle = ACPI_HANDLE(dev->dev);
140	if (!handle)
141		return 0;
142
143	status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
144	if (ACPI_FAILURE(status))
145		return 0;
146
147	if (shared_host) {
148		dev_info(dev->dev, "I2C bus managed by PUNIT\n");
149		dev->acquire_lock = baytrail_i2c_acquire;
150		dev->release_lock = baytrail_i2c_release;
151		dev->pm_runtime_disabled = true;
152	}
153
154	if (!iosf_mbi_available())
155		return -EPROBE_DEFER;
156
157	return 0;
158}
159
160MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");
161MODULE_DESCRIPTION("Baytrail I2C Semaphore driver");
162MODULE_LICENSE("GPL v2");
163