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, 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 
49 static 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 
65 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
66 {
67 	u32 sem;
68 	int ret;
69 	unsigned long start, end;
70 
71 	if (!dev || !dev->dev)
72 		return -ENODEV;
73 
74 	if (!dev->release_lock)
75 		return 0;
76 
77 	/* host driver writes to side band semaphore register */
78 	ret = iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE,
79 				PUNIT_SEMAPHORE, PUNIT_SEMAPHORE_ACQUIRE);
80 	if (ret) {
81 		dev_err(dev->dev, "iosf punit semaphore request failed\n");
82 		return ret;
83 	}
84 
85 	/* host driver waits for bit 0 to be set in semaphore register */
86 	start = jiffies;
87 	end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
88 	while (!time_after(jiffies, end)) {
89 		ret = get_sem(dev->dev, &sem);
90 		if (!ret && sem) {
91 			acquired = jiffies;
92 			dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
93 				jiffies_to_msecs(jiffies - start));
94 			return 0;
95 		}
96 
97 		usleep_range(1000, 2000);
98 	}
99 
100 	dev_err(dev->dev, "punit semaphore timed out, resetting\n");
101 	reset_semaphore(dev->dev);
102 
103 	ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,
104 				PUNIT_SEMAPHORE, &sem);
105 	if (ret)
106 		dev_err(dev->dev, "iosf failed to read punit semaphore\n");
107 	else
108 		dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
109 
110 	WARN_ON(1);
111 
112 	return -ETIMEDOUT;
113 }
114 
115 static void baytrail_i2c_release(struct dw_i2c_dev *dev)
116 {
117 	if (!dev || !dev->dev)
118 		return;
119 
120 	if (!dev->acquire_lock)
121 		return;
122 
123 	reset_semaphore(dev->dev);
124 	dev_dbg(dev->dev, "punit semaphore held for %ums\n",
125 		jiffies_to_msecs(jiffies - acquired));
126 }
127 
128 int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev)
129 {
130 	acpi_status status;
131 	unsigned long long shared_host = 0;
132 	acpi_handle handle;
133 
134 	if (!dev || !dev->dev)
135 		return 0;
136 
137 	handle = ACPI_HANDLE(dev->dev);
138 	if (!handle)
139 		return 0;
140 
141 	status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
142 	if (ACPI_FAILURE(status))
143 		return 0;
144 
145 	if (shared_host) {
146 		dev_info(dev->dev, "I2C bus managed by PUNIT\n");
147 		dev->acquire_lock = baytrail_i2c_acquire;
148 		dev->release_lock = baytrail_i2c_release;
149 		dev->pm_runtime_disabled = true;
150 	}
151 
152 	if (!iosf_mbi_available())
153 		return -EPROBE_DEFER;
154 
155 	return 0;
156 }
157 
158 MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");
159 MODULE_DESCRIPTION("Baytrail I2C Semaphore driver");
160 MODULE_LICENSE("GPL v2");
161