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 #include <asm/iosf_mbi.h>
  21 #include "i2c-designware-core.h"
  22
  23 #define SEMAPHORE_TIMEOUT       100
  24 #define PUNIT_SEMAPHORE         0x7
  25
  26 static unsigned long acquired;
  27
  28 static int get_sem(struct device *dev, u32 *sem)
  29 {
  30         u32 reg_val;
  31         int ret;
  32
  33         ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, PUNIT_SEMAPHORE,
  34                             &reg_val);
  35         if (ret) {
  36                 dev_err(dev, "iosf failed to read punit semaphore\n");
  37                 return ret;
  38         }
  39
  40         *sem = reg_val & 0x1;
  41
  42         return 0;
  43 }
  44
  45 static void reset_semaphore(struct device *dev)
  46 {
  47         u32 data;
  48
  49         if (iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,
  50                                 PUNIT_SEMAPHORE, &data)) {
  51                 dev_err(dev, "iosf failed to reset punit semaphore during read\n");
  52                 return;
  53         }
  54
  55         data = data & 0xfffffffe;
  56         if (iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE,
  57                                  PUNIT_SEMAPHORE, data))
  58                 dev_err(dev, "iosf failed to reset punit semaphore during write\n");
  59 }
  60
  61 int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
  62 {
  63         u32 sem = 0;
  64         int ret;
  65         unsigned long start, end;
  66
  67         if (!dev || !dev->dev)
  68                 return -ENODEV;
  69
  70         if (!dev->acquire_lock)
  71                 return 0;
  72
  73         /* host driver writes 0x2 to side band semaphore register */
  74         ret = iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE,
  75                                  PUNIT_SEMAPHORE, 0x2);
  76         if (ret) {
  77                 dev_err(dev->dev, "iosf punit semaphore request failed\n");
  78                 return ret;
  79         }
  80
  81         /* host driver waits for bit 0 to be set in semaphore register */
  82         start = jiffies;
  83         end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
  84         while (!time_after(jiffies, end)) {
  85                 ret = get_sem(dev->dev, &sem);
  86                 if (!ret && sem) {
  87                         acquired = jiffies;
  88                         dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
  89                                 jiffies_to_msecs(jiffies - start));
  90                         return 0;
  91                 }
  92
  93                 usleep_range(1000, 2000);
  94         }
  95
  96         dev_err(dev->dev, "punit semaphore timed out, resetting\n");
  97         reset_semaphore(dev->dev);
  98
  99         ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,
 100                 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 EXPORT_SYMBOL(baytrail_i2c_acquire);
 111
 112 void baytrail_i2c_release(struct dw_i2c_dev *dev)
 113 {
 114         if (!dev || !dev->dev)
 115                 return;
 116
 117         if (!dev->acquire_lock)
 118                 return;
 119
 120         reset_semaphore(dev->dev);
 121         dev_dbg(dev->dev, "punit semaphore held for %ums\n",
 122                 jiffies_to_msecs(jiffies - acquired));
 123 }
 124 EXPORT_SYMBOL(baytrail_i2c_release);
 125
 126 int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev)
 127 {
 128         acpi_status status;
 129         unsigned long long shared_host = 0;
 130         acpi_handle handle;
 131
 132         if (!dev || !dev->dev)
 133                 return 0;
 134
 135         handle = ACPI_HANDLE(dev->dev);
 136         if (!handle)
 137                 return 0;
 138
 139         status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
 140
 141         if (ACPI_FAILURE(status))
 142                 return 0;
 143
 144         if (shared_host) {
 145                 dev_info(dev->dev, "I2C bus managed by PUNIT\n");
 146                 dev->acquire_lock = baytrail_i2c_acquire;
 147                 dev->release_lock = baytrail_i2c_release;
 148                 dev->pm_runtime_disabled = true;
 149         }
 150
 151         if (!iosf_mbi_available())
 152                 return -EPROBE_DEFER;
 153
 154         return 0;
 155 }
 156 EXPORT_SYMBOL(i2c_dw_eval_lock_support);
 157
 158 MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");
 159 MODULE_DESCRIPTION("Baytrail I2C Semaphore driver");
 160 MODULE_LICENSE("GPL v2");