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, MBI_REG_READ, PUNIT_SEMAPHORE, &data);
  38         if (ret) {
  39                 dev_err(dev, "iosf failed to read punit semaphore\n");
  40                 return ret;
  41         }
  42
  43         *sem = data & PUNIT_SEMAPHORE_BIT;
  44
  45         return 0;
  46 }
  47
  48 static void reset_semaphore(struct device *dev)
  49 {
  50         u32 data;
  51
  52         if (iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, 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, MBI_REG_WRITE, PUNIT_SEMAPHORE, data))
  59                 dev_err(dev, "iosf failed to reset punit semaphore during write\n");
  60 }
  61
  62 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
  63 {
  64         u32 sem = PUNIT_SEMAPHORE_ACQUIRE;
  65         int ret;
  66         unsigned long start, end;
  67
  68         might_sleep();
  69
  70         if (!dev || !dev->dev)
  71                 return -ENODEV;
  72
  73         if (!dev->release_lock)
  74                 return 0;
  75
  76         /* host driver writes to side band semaphore register */
  77         ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, PUNIT_SEMAPHORE, sem);
  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         do {
  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         } while (time_before(jiffies, end));
  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, MBI_REG_READ, PUNIT_SEMAPHORE, &sem);
 102         if (ret)
 103                 dev_err(dev->dev, "iosf failed to read punit semaphore\n");
 104         else
 105                 dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
 106
 107         WARN_ON(1);
 108
 109         return -ETIMEDOUT;
 110 }
 111
 112 static 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
 125 int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev)
 126 {
 127         acpi_status status;
 128         unsigned long long shared_host = 0;
 129         acpi_handle handle;
 130
 131         if (!dev || !dev->dev)
 132                 return 0;
 133
 134         handle = ACPI_HANDLE(dev->dev);
 135         if (!handle)
 136                 return 0;
 137
 138         status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
 139         if (ACPI_FAILURE(status))
 140                 return 0;
 141
 142         if (shared_host) {
 143                 dev_info(dev->dev, "I2C bus managed by PUNIT\n");
 144                 dev->acquire_lock = baytrail_i2c_acquire;
 145                 dev->release_lock = baytrail_i2c_release;
 146                 dev->pm_runtime_disabled = true;
 147         }
 148
 149         if (!iosf_mbi_available())
 150                 return -EPROBE_DEFER;
 151
 152         return 0;
 153 }
 154
 155 MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");
 156 MODULE_DESCRIPTION("Baytrail I2C Semaphore driver");
 157 MODULE_LICENSE("GPL v2");