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 #include <asm/iosf_mbi.h> 21 #include "i2c-designware-core.h" 22 23 #define SEMAPHORE_TIMEOUT 100 24 #define PUNIT_SEMAPHORE 0x7 25 #define PUNIT_SEMAPHORE_BIT BIT(0) 26 #define PUNIT_SEMAPHORE_ACQUIRE BIT(1) 27 28 static unsigned long acquired; 29 30 static int get_sem(struct device *dev, u32 *sem) 31 { 32 u32 data; 33 int ret; 34 35 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, PUNIT_SEMAPHORE, 36 &data); 37 if (ret) { 38 dev_err(dev, "iosf failed to read punit semaphore\n"); 39 return ret; 40 } 41 42 *sem = data & PUNIT_SEMAPHORE_BIT; 43 44 return 0; 45 } 46 47 static void reset_semaphore(struct device *dev) 48 { 49 u32 data; 50 51 if (iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, 52 PUNIT_SEMAPHORE, &data)) { 53 dev_err(dev, "iosf failed to reset punit semaphore during read\n"); 54 return; 55 } 56 57 data &= ~PUNIT_SEMAPHORE_BIT; 58 if (iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE, 59 PUNIT_SEMAPHORE, data)) 60 dev_err(dev, "iosf failed to reset punit semaphore during write\n"); 61 } 62 63 int baytrail_i2c_acquire(struct dw_i2c_dev *dev) 64 { 65 u32 sem = 0; 66 int ret; 67 unsigned long start, end; 68 69 if (!dev || !dev->dev) 70 return -ENODEV; 71 72 if (!dev->acquire_lock) 73 return 0; 74 75 /* host driver writes to side band semaphore register */ 76 ret = iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE, 77 PUNIT_SEMAPHORE, PUNIT_SEMAPHORE_ACQUIRE); 78 if (ret) { 79 dev_err(dev->dev, "iosf punit semaphore request failed\n"); 80 return ret; 81 } 82 83 /* host driver waits for bit 0 to be set in semaphore register */ 84 start = jiffies; 85 end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT); 86 while (!time_after(jiffies, end)) { 87 ret = get_sem(dev->dev, &sem); 88 if (!ret && sem) { 89 acquired = jiffies; 90 dev_dbg(dev->dev, "punit semaphore acquired after %ums\n", 91 jiffies_to_msecs(jiffies - start)); 92 return 0; 93 } 94 95 usleep_range(1000, 2000); 96 } 97 98 dev_err(dev->dev, "punit semaphore timed out, resetting\n"); 99 reset_semaphore(dev->dev); 100 101 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, 102 PUNIT_SEMAPHORE, &sem); 103 if (ret) 104 dev_err(dev->dev, "iosf failed to read punit semaphore\n"); 105 else 106 dev_err(dev->dev, "PUNIT SEM: %d\n", sem); 107 108 WARN_ON(1); 109 110 return -ETIMEDOUT; 111 } 112 EXPORT_SYMBOL(baytrail_i2c_acquire); 113 114 void baytrail_i2c_release(struct dw_i2c_dev *dev) 115 { 116 if (!dev || !dev->dev) 117 return; 118 119 if (!dev->acquire_lock) 120 return; 121 122 reset_semaphore(dev->dev); 123 dev_dbg(dev->dev, "punit semaphore held for %ums\n", 124 jiffies_to_msecs(jiffies - acquired)); 125 } 126 EXPORT_SYMBOL(baytrail_i2c_release); 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); 142 143 if (ACPI_FAILURE(status)) 144 return 0; 145 146 if (shared_host) { 147 dev_info(dev->dev, "I2C bus managed by PUNIT\n"); 148 dev->acquire_lock = baytrail_i2c_acquire; 149 dev->release_lock = baytrail_i2c_release; 150 dev->pm_runtime_disabled = true; 151 } 152 153 if (!iosf_mbi_available()) 154 return -EPROBE_DEFER; 155 156 return 0; 157 } 158 EXPORT_SYMBOL(i2c_dw_eval_lock_support); 159 160 MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>"); 161 MODULE_DESCRIPTION("Baytrail I2C Semaphore driver"); 162 MODULE_LICENSE("GPL v2"); 163