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       500
  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_call_pmic_bus_access_notifier_chain(MBI_PMIC_BUS_ACCESS_END,
  67                                                      NULL);
  68         iosf_mbi_punit_release();
  69 }
  70
  71 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
  72 {
  73         u32 addr;
  74         u32 sem = PUNIT_SEMAPHORE_ACQUIRE;
  75         int ret;
  76         unsigned long start, end;
  77
  78         might_sleep();
  79
  80         if (!dev || !dev->dev)
  81                 return -ENODEV;
  82
  83         if (!dev->release_lock)
  84                 return 0;
  85
  86         iosf_mbi_punit_acquire();
  87         iosf_mbi_call_pmic_bus_access_notifier_chain(MBI_PMIC_BUS_ACCESS_BEGIN,
  88                                                      NULL);
  89
  90         /*
  91          * Disallow the CPU to enter C6 or C7 state, entering these states
  92          * requires the punit to talk to the pmic and if this happens while
  93          * we're holding the semaphore, the SoC hangs.
  94          */
  95         pm_qos_update_request(&dev->pm_qos, 0);
  96
  97         addr = get_sem_addr(dev);
  98
  99         /* host driver writes to side band semaphore register */
 100         ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, addr, sem);
 101         if (ret) {
 102                 dev_err(dev->dev, "iosf punit semaphore request failed\n");
 103                 goto out;
 104         }
 105
 106         /* host driver waits for bit 0 to be set in semaphore register */
 107         start = jiffies;
 108         end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
 109         do {
 110                 ret = get_sem(dev, &sem);
 111                 if (!ret && sem) {
 112                         acquired = jiffies;
 113                         dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
 114                                 jiffies_to_msecs(jiffies - start));
 115                         return 0;
 116                 }
 117
 118                 usleep_range(1000, 2000);
 119         } while (time_before(jiffies, end));
 120
 121         dev_err(dev->dev, "punit semaphore timed out, resetting\n");
 122 out:
 123         reset_semaphore(dev);
 124
 125         ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &sem);
 126         if (ret)
 127                 dev_err(dev->dev, "iosf failed to read punit semaphore\n");
 128         else
 129                 dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
 130
 131         WARN_ON(1);
 132
 133         return -ETIMEDOUT;
 134 }
 135
 136 static void baytrail_i2c_release(struct dw_i2c_dev *dev)
 137 {
 138         if (!dev || !dev->dev)
 139                 return;
 140
 141         if (!dev->acquire_lock)
 142                 return;
 143
 144         reset_semaphore(dev);
 145         dev_dbg(dev->dev, "punit semaphore held for %ums\n",
 146                 jiffies_to_msecs(jiffies - acquired));
 147 }
 148
 149 int i2c_dw_probe_lock_support(struct dw_i2c_dev *dev)
 150 {
 151         acpi_status status;
 152         unsigned long long shared_host = 0;
 153         acpi_handle handle;
 154
 155         if (!dev || !dev->dev)
 156                 return 0;
 157
 158         handle = ACPI_HANDLE(dev->dev);
 159         if (!handle)
 160                 return 0;
 161
 162         status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
 163         if (ACPI_FAILURE(status))
 164                 return 0;
 165
 166         if (!shared_host)
 167                 return 0;
 168
 169         if (!iosf_mbi_available())
 170                 return -EPROBE_DEFER;
 171
 172         dev_info(dev->dev, "I2C bus managed by PUNIT\n");
 173         dev->acquire_lock = baytrail_i2c_acquire;
 174         dev->release_lock = baytrail_i2c_release;
 175         dev->pm_disabled = true;
 176
 177         pm_qos_add_request(&dev->pm_qos, PM_QOS_CPU_DMA_LATENCY,
 178                            PM_QOS_DEFAULT_VALUE);
 179
 180         return 0;
 181 }
 182
 183 void i2c_dw_remove_lock_support(struct dw_i2c_dev *dev)
 184 {
 185         if (dev->acquire_lock)
 186                 pm_qos_remove_request(&dev->pm_qos);
 187 }