drivers/i2c/busses/i2c-designware-baytrail.c

   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");