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 100 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 67 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev) 68 { 69 u32 addr = get_sem_addr(dev); 70 u32 sem = PUNIT_SEMAPHORE_ACQUIRE; 71 int ret; 72 unsigned long start, end; 73 74 might_sleep(); 75 76 if (!dev || !dev->dev) 77 return -ENODEV; 78 79 if (!dev->release_lock) 80 return 0; 81 82 /* 83 * Disallow the CPU to enter C6 or C7 state, entering these states 84 * requires the punit to talk to the pmic and if this happens while 85 * we're holding the semaphore, the SoC hangs. 86 */ 87 pm_qos_update_request(&dev->pm_qos, 0); 88 89 /* host driver writes to side band semaphore register */ 90 ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, addr, sem); 91 if (ret) { 92 dev_err(dev->dev, "iosf punit semaphore request failed\n"); 93 goto out; 94 } 95 96 /* host driver waits for bit 0 to be set in semaphore register */ 97 start = jiffies; 98 end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT); 99 do { 100 ret = get_sem(dev, &sem); 101 if (!ret && sem) { 102 acquired = jiffies; 103 dev_dbg(dev->dev, "punit semaphore acquired after %ums\n", 104 jiffies_to_msecs(jiffies - start)); 105 return 0; 106 } 107 108 usleep_range(1000, 2000); 109 } while (time_before(jiffies, end)); 110 111 dev_err(dev->dev, "punit semaphore timed out, resetting\n"); 112 out: 113 reset_semaphore(dev); 114 115 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &sem); 116 if (ret) 117 dev_err(dev->dev, "iosf failed to read punit semaphore\n"); 118 else 119 dev_err(dev->dev, "PUNIT SEM: %d\n", sem); 120 121 WARN_ON(1); 122 123 return -ETIMEDOUT; 124 } 125 126 static void baytrail_i2c_release(struct dw_i2c_dev *dev) 127 { 128 if (!dev || !dev->dev) 129 return; 130 131 if (!dev->acquire_lock) 132 return; 133 134 reset_semaphore(dev); 135 dev_dbg(dev->dev, "punit semaphore held for %ums\n", 136 jiffies_to_msecs(jiffies - acquired)); 137 } 138 139 int i2c_dw_probe_lock_support(struct dw_i2c_dev *dev) 140 { 141 acpi_status status; 142 unsigned long long shared_host = 0; 143 acpi_handle handle; 144 145 if (!dev || !dev->dev) 146 return 0; 147 148 handle = ACPI_HANDLE(dev->dev); 149 if (!handle) 150 return 0; 151 152 status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host); 153 if (ACPI_FAILURE(status)) 154 return 0; 155 156 if (!shared_host) 157 return 0; 158 159 if (!iosf_mbi_available()) 160 return -EPROBE_DEFER; 161 162 dev_info(dev->dev, "I2C bus managed by PUNIT\n"); 163 dev->acquire_lock = baytrail_i2c_acquire; 164 dev->release_lock = baytrail_i2c_release; 165 dev->pm_runtime_disabled = true; 166 167 pm_qos_add_request(&dev->pm_qos, PM_QOS_CPU_DMA_LATENCY, 168 PM_QOS_DEFAULT_VALUE); 169 170 return 0; 171 } 172 173 void i2c_dw_remove_lock_support(struct dw_i2c_dev *dev) 174 { 175 if (dev->acquire_lock) 176 pm_qos_remove_request(&dev->pm_qos); 177 } 178