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 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_BIT BIT(0) 28 #define PUNIT_SEMAPHORE_ACQUIRE BIT(1) 29 30 static unsigned long acquired; 31 32 static int get_sem(struct device *dev, u32 *sem) 33 { 34 u32 data; 35 int ret; 36 37 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, PUNIT_SEMAPHORE, 38 &data); 39 if (ret) { 40 dev_err(dev, "iosf failed to read punit semaphore\n"); 41 return ret; 42 } 43 44 *sem = data & PUNIT_SEMAPHORE_BIT; 45 46 return 0; 47 } 48 49 static void reset_semaphore(struct device *dev) 50 { 51 u32 data; 52 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"); 56 return; 57 } 58 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"); 63 } 64 65 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev) 66 { 67 u32 sem; 68 int ret; 69 unsigned long start, end; 70 71 might_sleep(); 72 73 if (!dev || !dev->dev) 74 return -ENODEV; 75 76 if (!dev->release_lock) 77 return 0; 78 79 /* host driver writes to side band semaphore register */ 80 ret = iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE, 81 PUNIT_SEMAPHORE, PUNIT_SEMAPHORE_ACQUIRE); 82 if (ret) { 83 dev_err(dev->dev, "iosf punit semaphore request failed\n"); 84 return ret; 85 } 86 87 /* host driver waits for bit 0 to be set in semaphore register */ 88 start = jiffies; 89 end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT); 90 do { 91 ret = get_sem(dev->dev, &sem); 92 if (!ret && sem) { 93 acquired = jiffies; 94 dev_dbg(dev->dev, "punit semaphore acquired after %ums\n", 95 jiffies_to_msecs(jiffies - start)); 96 return 0; 97 } 98 99 usleep_range(1000, 2000); 100 } while (time_before(jiffies, end)); 101 102 dev_err(dev->dev, "punit semaphore timed out, resetting\n"); 103 reset_semaphore(dev->dev); 104 105 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, 106 PUNIT_SEMAPHORE, &sem); 107 if (ret) 108 dev_err(dev->dev, "iosf failed to read punit semaphore\n"); 109 else 110 dev_err(dev->dev, "PUNIT SEM: %d\n", sem); 111 112 WARN_ON(1); 113 114 return -ETIMEDOUT; 115 } 116 117 static void baytrail_i2c_release(struct dw_i2c_dev *dev) 118 { 119 if (!dev || !dev->dev) 120 return; 121 122 if (!dev->acquire_lock) 123 return; 124 125 reset_semaphore(dev->dev); 126 dev_dbg(dev->dev, "punit semaphore held for %ums\n", 127 jiffies_to_msecs(jiffies - acquired)); 128 } 129 130 int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev) 131 { 132 acpi_status status; 133 unsigned long long shared_host = 0; 134 acpi_handle handle; 135 136 if (!dev || !dev->dev) 137 return 0; 138 139 handle = ACPI_HANDLE(dev->dev); 140 if (!handle) 141 return 0; 142 143 status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host); 144 if (ACPI_FAILURE(status)) 145 return 0; 146 147 if (shared_host) { 148 dev_info(dev->dev, "I2C bus managed by PUNIT\n"); 149 dev->acquire_lock = baytrail_i2c_acquire; 150 dev->release_lock = baytrail_i2c_release; 151 dev->pm_runtime_disabled = true; 152 } 153 154 if (!iosf_mbi_available()) 155 return -EPROBE_DEFER; 156 157 return 0; 158 } 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