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/delay.h>
15 #include <linux/device.h>
16 #include <linux/acpi.h>
17 #include <linux/i2c.h>
18 #include <linux/interrupt.h>
19 #include <linux/pm_qos.h>
21 #include <asm/iosf_mbi.h>
23 #include "i2c-designware-core.h"
25 #define SEMAPHORE_TIMEOUT 500
26 #define PUNIT_SEMAPHORE 0x7
27 #define PUNIT_SEMAPHORE_CHT 0x10e
28 #define PUNIT_SEMAPHORE_BIT BIT(0)
29 #define PUNIT_SEMAPHORE_ACQUIRE BIT(1)
31 static unsigned long acquired;
33 static u32 get_sem_addr(struct dw_i2c_dev *dev)
35 if (dev->flags & MODEL_CHERRYTRAIL)
36 return PUNIT_SEMAPHORE_CHT;
38 return PUNIT_SEMAPHORE;
41 static int get_sem(struct dw_i2c_dev *dev, u32 *sem)
43 u32 addr = get_sem_addr(dev);
47 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &data);
49 dev_err(dev->dev, "iosf failed to read punit semaphore\n");
53 *sem = data & PUNIT_SEMAPHORE_BIT;
58 static void reset_semaphore(struct dw_i2c_dev *dev)
60 if (iosf_mbi_modify(BT_MBI_UNIT_PMC, MBI_REG_READ, get_sem_addr(dev),
61 0, PUNIT_SEMAPHORE_BIT))
62 dev_err(dev->dev, "iosf failed to reset punit semaphore during write\n");
64 pm_qos_update_request(&dev->pm_qos, PM_QOS_DEFAULT_VALUE);
66 iosf_mbi_call_pmic_bus_access_notifier_chain(MBI_PMIC_BUS_ACCESS_END,
68 iosf_mbi_punit_release();
71 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
74 u32 sem = PUNIT_SEMAPHORE_ACQUIRE;
76 unsigned long start, end;
80 if (!dev || !dev->dev)
83 if (!dev->release_lock)
86 iosf_mbi_punit_acquire();
87 iosf_mbi_call_pmic_bus_access_notifier_chain(MBI_PMIC_BUS_ACCESS_BEGIN,
91 * Disallow the CPU to enter C6 or C7 state, entering these states
92 * requires the punit to talk to the pmic and if this happens while
93 * we're holding the semaphore, the SoC hangs.
95 pm_qos_update_request(&dev->pm_qos, 0);
97 addr = get_sem_addr(dev);
99 /* host driver writes to side band semaphore register */
100 ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, addr, sem);
102 dev_err(dev->dev, "iosf punit semaphore request failed\n");
106 /* host driver waits for bit 0 to be set in semaphore register */
108 end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
110 ret = get_sem(dev, &sem);
113 dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
114 jiffies_to_msecs(jiffies - start));
118 usleep_range(1000, 2000);
119 } while (time_before(jiffies, end));
121 dev_err(dev->dev, "punit semaphore timed out, resetting\n");
123 reset_semaphore(dev);
125 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &sem);
127 dev_err(dev->dev, "iosf failed to read punit semaphore\n");
129 dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
136 static void baytrail_i2c_release(struct dw_i2c_dev *dev)
138 if (!dev || !dev->dev)
141 if (!dev->acquire_lock)
144 reset_semaphore(dev);
145 dev_dbg(dev->dev, "punit semaphore held for %ums\n",
146 jiffies_to_msecs(jiffies - acquired));
149 int i2c_dw_probe_lock_support(struct dw_i2c_dev *dev)
152 unsigned long long shared_host = 0;
155 if (!dev || !dev->dev)
158 handle = ACPI_HANDLE(dev->dev);
162 status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
163 if (ACPI_FAILURE(status))
169 if (!iosf_mbi_available())
170 return -EPROBE_DEFER;
172 dev_info(dev->dev, "I2C bus managed by PUNIT\n");
173 dev->acquire_lock = baytrail_i2c_acquire;
174 dev->release_lock = baytrail_i2c_release;
175 dev->pm_disabled = true;
177 pm_qos_add_request(&dev->pm_qos, PM_QOS_CPU_DMA_LATENCY,
178 PM_QOS_DEFAULT_VALUE);
183 void i2c_dw_remove_lock_support(struct dw_i2c_dev *dev)
185 if (dev->acquire_lock)
186 pm_qos_remove_request(&dev->pm_qos);