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/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 device *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, "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 device *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, "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, "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->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->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->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                 dev_info(dev->dev, "I2C bus managed by PUNIT\n");
 143                 dev->acquire_lock = baytrail_i2c_acquire;
 144                 dev->release_lock = baytrail_i2c_release;
 145                 dev->pm_runtime_disabled = true;
 146         }
 147
 148         if (!iosf_mbi_available())
 149                 return -EPROBE_DEFER;
 150
 151         return 0;
 152 }