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 20 #include <asm/iosf_mbi.h> 21 22 #include "i2c-designware-core.h" 23 24 #define SEMAPHORE_TIMEOUT 100 25 #define PUNIT_SEMAPHORE 0x7 26 #define PUNIT_SEMAPHORE_BIT BIT(0) 27 #define PUNIT_SEMAPHORE_ACQUIRE BIT(1) 28 29 static unsigned long acquired; 30 31 static int get_sem(struct dw_i2c_dev *dev, u32 *sem) 32 { 33 u32 data; 34 int ret; 35 36 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, PUNIT_SEMAPHORE, &data); 37 if (ret) { 38 dev_err(dev->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 dw_i2c_dev *dev) 48 { 49 u32 data; 50 51 if (iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, PUNIT_SEMAPHORE, &data)) { 52 dev_err(dev->dev, "iosf failed to reset punit semaphore during read\n"); 53 return; 54 } 55 56 data &= ~PUNIT_SEMAPHORE_BIT; 57 if (iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, PUNIT_SEMAPHORE, data)) 58 dev_err(dev->dev, "iosf failed to reset punit semaphore during write\n"); 59 } 60 61 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev) 62 { 63 u32 sem = PUNIT_SEMAPHORE_ACQUIRE; 64 int ret; 65 unsigned long start, end; 66 67 might_sleep(); 68 69 if (!dev || !dev->dev) 70 return -ENODEV; 71 72 if (!dev->release_lock) 73 return 0; 74 75 /* host driver writes to side band semaphore register */ 76 ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, PUNIT_SEMAPHORE, sem); 77 if (ret) { 78 dev_err(dev->dev, "iosf punit semaphore request failed\n"); 79 return ret; 80 } 81 82 /* host driver waits for bit 0 to be set in semaphore register */ 83 start = jiffies; 84 end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT); 85 do { 86 ret = get_sem(dev, &sem); 87 if (!ret && sem) { 88 acquired = jiffies; 89 dev_dbg(dev->dev, "punit semaphore acquired after %ums\n", 90 jiffies_to_msecs(jiffies - start)); 91 return 0; 92 } 93 94 usleep_range(1000, 2000); 95 } while (time_before(jiffies, end)); 96 97 dev_err(dev->dev, "punit semaphore timed out, resetting\n"); 98 reset_semaphore(dev); 99 100 ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, PUNIT_SEMAPHORE, &sem); 101 if (ret) 102 dev_err(dev->dev, "iosf failed to read punit semaphore\n"); 103 else 104 dev_err(dev->dev, "PUNIT SEM: %d\n", sem); 105 106 WARN_ON(1); 107 108 return -ETIMEDOUT; 109 } 110 111 static void baytrail_i2c_release(struct dw_i2c_dev *dev) 112 { 113 if (!dev || !dev->dev) 114 return; 115 116 if (!dev->acquire_lock) 117 return; 118 119 reset_semaphore(dev); 120 dev_dbg(dev->dev, "punit semaphore held for %ums\n", 121 jiffies_to_msecs(jiffies - acquired)); 122 } 123 124 int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev) 125 { 126 acpi_status status; 127 unsigned long long shared_host = 0; 128 acpi_handle handle; 129 130 if (!dev || !dev->dev) 131 return 0; 132 133 handle = ACPI_HANDLE(dev->dev); 134 if (!handle) 135 return 0; 136 137 status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host); 138 if (ACPI_FAILURE(status)) 139 return 0; 140 141 if (!shared_host) 142 return 0; 143 144 if (!iosf_mbi_available()) 145 return -EPROBE_DEFER; 146 147 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 return 0; 153 } 154