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 
30 static unsigned long acquired;
31 
32 static 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, MBI_REG_READ, PUNIT_SEMAPHORE, &data);
38 	if (ret) {
39 		dev_err(dev, "iosf failed to read punit semaphore\n");
40 		return ret;
41 	}
42 
43 	*sem = data & PUNIT_SEMAPHORE_BIT;
44 
45 	return 0;
46 }
47 
48 static void reset_semaphore(struct device *dev)
49 {
50 	u32 data;
51 
52 	if (iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, PUNIT_SEMAPHORE, &data)) {
53 		dev_err(dev, "iosf failed to reset punit semaphore during read\n");
54 		return;
55 	}
56 
57 	data &= ~PUNIT_SEMAPHORE_BIT;
58 	if (iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, PUNIT_SEMAPHORE, data))
59 		dev_err(dev, "iosf failed to reset punit semaphore during write\n");
60 }
61 
62 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
63 {
64 	u32 sem = PUNIT_SEMAPHORE_ACQUIRE;
65 	int ret;
66 	unsigned long start, end;
67 
68 	might_sleep();
69 
70 	if (!dev || !dev->dev)
71 		return -ENODEV;
72 
73 	if (!dev->release_lock)
74 		return 0;
75 
76 	/* host driver writes to side band semaphore register */
77 	ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, PUNIT_SEMAPHORE, sem);
78 	if (ret) {
79 		dev_err(dev->dev, "iosf punit semaphore request failed\n");
80 		return ret;
81 	}
82 
83 	/* host driver waits for bit 0 to be set in semaphore register */
84 	start = jiffies;
85 	end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
86 	do {
87 		ret = get_sem(dev->dev, &sem);
88 		if (!ret && sem) {
89 			acquired = jiffies;
90 			dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
91 				jiffies_to_msecs(jiffies - start));
92 			return 0;
93 		}
94 
95 		usleep_range(1000, 2000);
96 	} while (time_before(jiffies, end));
97 
98 	dev_err(dev->dev, "punit semaphore timed out, resetting\n");
99 	reset_semaphore(dev->dev);
100 
101 	ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, PUNIT_SEMAPHORE, &sem);
102 	if (ret)
103 		dev_err(dev->dev, "iosf failed to read punit semaphore\n");
104 	else
105 		dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
106 
107 	WARN_ON(1);
108 
109 	return -ETIMEDOUT;
110 }
111 
112 static void baytrail_i2c_release(struct dw_i2c_dev *dev)
113 {
114 	if (!dev || !dev->dev)
115 		return;
116 
117 	if (!dev->acquire_lock)
118 		return;
119 
120 	reset_semaphore(dev->dev);
121 	dev_dbg(dev->dev, "punit semaphore held for %ums\n",
122 		jiffies_to_msecs(jiffies - acquired));
123 }
124 
125 int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev)
126 {
127 	acpi_status status;
128 	unsigned long long shared_host = 0;
129 	acpi_handle handle;
130 
131 	if (!dev || !dev->dev)
132 		return 0;
133 
134 	handle = ACPI_HANDLE(dev->dev);
135 	if (!handle)
136 		return 0;
137 
138 	status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
139 	if (ACPI_FAILURE(status))
140 		return 0;
141 
142 	if (shared_host) {
143 		dev_info(dev->dev, "I2C bus managed by PUNIT\n");
144 		dev->acquire_lock = baytrail_i2c_acquire;
145 		dev->release_lock = baytrail_i2c_release;
146 		dev->pm_runtime_disabled = true;
147 	}
148 
149 	if (!iosf_mbi_available())
150 		return -EPROBE_DEFER;
151 
152 	return 0;
153 }
154 
155 MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");
156 MODULE_DESCRIPTION("Baytrail I2C Semaphore driver");
157 MODULE_LICENSE("GPL v2");
158