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/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> 20 21 #include <asm/iosf_mbi.h> 22 23 #include "i2c-designware-core.h" 24 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) 30 31 static unsigned long acquired; 32 33 static u32 get_sem_addr(struct dw_i2c_dev *dev) 34 { 35 if (dev->flags & MODEL_CHERRYTRAIL) 36 return PUNIT_SEMAPHORE_CHT; 37 else 38 return PUNIT_SEMAPHORE; 39 } 40 41 static int get_sem(struct dw_i2c_dev *dev, u32 *sem) 42 { 43 u32 addr = get_sem_addr(dev); 44 u32 data; 45 int ret; 46 47 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &data); 48 if (ret) { 49 dev_err(dev->dev, "iosf failed to read punit semaphore\n"); 50 return ret; 51 } 52 53 *sem = data & PUNIT_SEMAPHORE_BIT; 54 55 return 0; 56 } 57 58 static void reset_semaphore(struct dw_i2c_dev *dev) 59 { 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"); 63 64 pm_qos_update_request(&dev->pm_qos, PM_QOS_DEFAULT_VALUE); 65 66 iosf_mbi_call_pmic_bus_access_notifier_chain(MBI_PMIC_BUS_ACCESS_END, 67 NULL); 68 iosf_mbi_punit_release(); 69 } 70 71 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev) 72 { 73 u32 addr; 74 u32 sem = PUNIT_SEMAPHORE_ACQUIRE; 75 int ret; 76 unsigned long start, end; 77 78 might_sleep(); 79 80 if (!dev || !dev->dev) 81 return -ENODEV; 82 83 if (!dev->release_lock) 84 return 0; 85 86 iosf_mbi_punit_acquire(); 87 iosf_mbi_call_pmic_bus_access_notifier_chain(MBI_PMIC_BUS_ACCESS_BEGIN, 88 NULL); 89 90 /* 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. 94 */ 95 pm_qos_update_request(&dev->pm_qos, 0); 96 97 addr = get_sem_addr(dev); 98 99 /* host driver writes to side band semaphore register */ 100 ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, addr, sem); 101 if (ret) { 102 dev_err(dev->dev, "iosf punit semaphore request failed\n"); 103 goto out; 104 } 105 106 /* host driver waits for bit 0 to be set in semaphore register */ 107 start = jiffies; 108 end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT); 109 do { 110 ret = get_sem(dev, &sem); 111 if (!ret && sem) { 112 acquired = jiffies; 113 dev_dbg(dev->dev, "punit semaphore acquired after %ums\n", 114 jiffies_to_msecs(jiffies - start)); 115 return 0; 116 } 117 118 usleep_range(1000, 2000); 119 } while (time_before(jiffies, end)); 120 121 dev_err(dev->dev, "punit semaphore timed out, resetting\n"); 122 out: 123 reset_semaphore(dev); 124 125 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &sem); 126 if (ret) 127 dev_err(dev->dev, "iosf failed to read punit semaphore\n"); 128 else 129 dev_err(dev->dev, "PUNIT SEM: %d\n", sem); 130 131 WARN_ON(1); 132 133 return -ETIMEDOUT; 134 } 135 136 static void baytrail_i2c_release(struct dw_i2c_dev *dev) 137 { 138 if (!dev || !dev->dev) 139 return; 140 141 if (!dev->acquire_lock) 142 return; 143 144 reset_semaphore(dev); 145 dev_dbg(dev->dev, "punit semaphore held for %ums\n", 146 jiffies_to_msecs(jiffies - acquired)); 147 } 148 149 int i2c_dw_probe_lock_support(struct dw_i2c_dev *dev) 150 { 151 acpi_status status; 152 unsigned long long shared_host = 0; 153 acpi_handle handle; 154 155 if (!dev || !dev->dev) 156 return 0; 157 158 handle = ACPI_HANDLE(dev->dev); 159 if (!handle) 160 return 0; 161 162 status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host); 163 if (ACPI_FAILURE(status)) 164 return 0; 165 166 if (!shared_host) 167 return 0; 168 169 if (!iosf_mbi_available()) 170 return -EPROBE_DEFER; 171 172 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; 176 177 pm_qos_add_request(&dev->pm_qos, PM_QOS_CPU_DMA_LATENCY, 178 PM_QOS_DEFAULT_VALUE); 179 180 return 0; 181 } 182 183 void i2c_dw_remove_lock_support(struct dw_i2c_dev *dev) 184 { 185 if (dev->acquire_lock) 186 pm_qos_remove_request(&dev->pm_qos); 187 } 188