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 #include <linux/pm_qos.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_CHT     0x10e
  28 #define PUNIT_SEMAPHORE_BIT     BIT(0)
  29 #define PUNIT_SEMAPHORE_ACQUIRE BIT(1)
  30
  31 static unsigned long acquired;
  32
  33 static u32 get_sem_addr(struct dw_i2c_dev *dev)
  34 {
  35         if (dev->flags & MODEL_CHERRYTRAIL)
  36                 return PUNIT_SEMAPHORE_CHT;
  37         else
  38                 return PUNIT_SEMAPHORE;
  39 }
  40
  41 static int get_sem(struct dw_i2c_dev *dev, u32 *sem)
  42 {
  43         u32 addr = get_sem_addr(dev);
  44         u32 data;
  45         int ret;
  46
  47         ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &data);
  48         if (ret) {
  49                 dev_err(dev->dev, "iosf failed to read punit semaphore\n");
  50                 return ret;
  51         }
  52
  53         *sem = data & PUNIT_SEMAPHORE_BIT;
  54
  55         return 0;
  56 }
  57
  58 static void reset_semaphore(struct dw_i2c_dev *dev)
  59 {
  60         if (iosf_mbi_modify(BT_MBI_UNIT_PMC, MBI_REG_READ, get_sem_addr(dev),
  61                             0, PUNIT_SEMAPHORE_BIT))
  62                 dev_err(dev->dev, "iosf failed to reset punit semaphore during write\n");
  63
  64         pm_qos_update_request(&dev->pm_qos, PM_QOS_DEFAULT_VALUE);
  65
  66         iosf_mbi_punit_release();
  67 }
  68
  69 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
  70 {
  71         u32 addr = get_sem_addr(dev);
  72         u32 sem = PUNIT_SEMAPHORE_ACQUIRE;
  73         int ret;
  74         unsigned long start, end;
  75
  76         might_sleep();
  77
  78         if (!dev || !dev->dev)
  79                 return -ENODEV;
  80
  81         if (!dev->release_lock)
  82                 return 0;
  83
  84         iosf_mbi_punit_acquire();
  85
  86         /*
  87          * Disallow the CPU to enter C6 or C7 state, entering these states
  88          * requires the punit to talk to the pmic and if this happens while
  89          * we're holding the semaphore, the SoC hangs.
  90          */
  91         pm_qos_update_request(&dev->pm_qos, 0);
  92
  93         /* host driver writes to side band semaphore register */
  94         ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, addr, sem);
  95         if (ret) {
  96                 dev_err(dev->dev, "iosf punit semaphore request failed\n");
  97                 goto out;
  98         }
  99
 100         /* host driver waits for bit 0 to be set in semaphore register */
 101         start = jiffies;
 102         end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
 103         do {
 104                 ret = get_sem(dev, &sem);
 105                 if (!ret && sem) {
 106                         acquired = jiffies;
 107                         dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
 108                                 jiffies_to_msecs(jiffies - start));
 109                         return 0;
 110                 }
 111
 112                 usleep_range(1000, 2000);
 113         } while (time_before(jiffies, end));
 114
 115         dev_err(dev->dev, "punit semaphore timed out, resetting\n");
 116 out:
 117         reset_semaphore(dev);
 118
 119         ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &sem);
 120         if (ret)
 121                 dev_err(dev->dev, "iosf failed to read punit semaphore\n");
 122         else
 123                 dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
 124
 125         WARN_ON(1);
 126
 127         return -ETIMEDOUT;
 128 }
 129
 130 static void baytrail_i2c_release(struct dw_i2c_dev *dev)
 131 {
 132         if (!dev || !dev->dev)
 133                 return;
 134
 135         if (!dev->acquire_lock)
 136                 return;
 137
 138         reset_semaphore(dev);
 139         dev_dbg(dev->dev, "punit semaphore held for %ums\n",
 140                 jiffies_to_msecs(jiffies - acquired));
 141 }
 142
 143 int i2c_dw_probe_lock_support(struct dw_i2c_dev *dev)
 144 {
 145         acpi_status status;
 146         unsigned long long shared_host = 0;
 147         acpi_handle handle;
 148
 149         if (!dev || !dev->dev)
 150                 return 0;
 151
 152         handle = ACPI_HANDLE(dev->dev);
 153         if (!handle)
 154                 return 0;
 155
 156         status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
 157         if (ACPI_FAILURE(status))
 158                 return 0;
 159
 160         if (!shared_host)
 161                 return 0;
 162
 163         if (!iosf_mbi_available())
 164                 return -EPROBE_DEFER;
 165
 166         dev_info(dev->dev, "I2C bus managed by PUNIT\n");
 167         dev->acquire_lock = baytrail_i2c_acquire;
 168         dev->release_lock = baytrail_i2c_release;
 169         dev->pm_runtime_disabled = true;
 170
 171         pm_qos_add_request(&dev->pm_qos, PM_QOS_CPU_DMA_LATENCY,
 172                            PM_QOS_DEFAULT_VALUE);
 173
 174         return 0;
 175 }
 176
 177 void i2c_dw_remove_lock_support(struct dw_i2c_dev *dev)
 178 {
 179         if (dev->acquire_lock)
 180                 pm_qos_remove_request(&dev->pm_qos);
 181 }