2 * Intel BayTrail PMIC I2C bus semaphore implementaion
3 * Copyright (c) 2014, Intel Corporation.
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.
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
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>
21 #include <asm/iosf_mbi.h>
23 #include "i2c-designware-core.h"
25 #define SEMAPHORE_TIMEOUT 100
26 #define PUNIT_SEMAPHORE 0x7
27 #define PUNIT_SEMAPHORE_BIT BIT(0)
28 #define PUNIT_SEMAPHORE_ACQUIRE BIT(1)
30 static unsigned long acquired;
32 static int get_sem(struct device *dev, u32 *sem)
37 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, PUNIT_SEMAPHORE,
40 dev_err(dev, "iosf failed to read punit semaphore\n");
44 *sem = data & PUNIT_SEMAPHORE_BIT;
49 static void reset_semaphore(struct device *dev)
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");
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");
65 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
69 unsigned long start, end;
71 if (!dev || !dev->dev)
74 if (!dev->acquire_lock)
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);
81 dev_err(dev->dev, "iosf punit semaphore request failed\n");
85 /* host driver waits for bit 0 to be set in semaphore register */
87 end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
88 while (!time_after(jiffies, end)) {
89 ret = get_sem(dev->dev, &sem);
92 dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
93 jiffies_to_msecs(jiffies - start));
97 usleep_range(1000, 2000);
100 dev_err(dev->dev, "punit semaphore timed out, resetting\n");
101 reset_semaphore(dev->dev);
103 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,
104 PUNIT_SEMAPHORE, &sem);
106 dev_err(dev->dev, "iosf failed to read punit semaphore\n");
108 dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
115 static void baytrail_i2c_release(struct dw_i2c_dev *dev)
117 if (!dev || !dev->dev)
120 if (!dev->acquire_lock)
123 reset_semaphore(dev->dev);
124 dev_dbg(dev->dev, "punit semaphore held for %ums\n",
125 jiffies_to_msecs(jiffies - acquired));
128 int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev)
131 unsigned long long shared_host = 0;
134 if (!dev || !dev->dev)
137 handle = ACPI_HANDLE(dev->dev);
141 status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
142 if (ACPI_FAILURE(status))
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;
152 if (!iosf_mbi_available())
153 return -EPROBE_DEFER;
158 MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");
159 MODULE_DESCRIPTION("Baytrail I2C Semaphore driver");
160 MODULE_LICENSE("GPL v2");