drivers/i2c/busses/i2c-designware-baytrail.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Intel BayTrail PMIC I2C bus semaphore implementaion
   4  * Copyright (c) 2014, Intel Corporation.
   5  */
   6 #include <linux/delay.h>
   7 #include <linux/device.h>
   8 #include <linux/acpi.h>
   9 #include <linux/i2c.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/pm_qos.h>
  12
  13 #include <asm/iosf_mbi.h>
  14
  15 #include "i2c-designware-core.h"
  16
  17 #define SEMAPHORE_TIMEOUT       500
  18 #define PUNIT_SEMAPHORE         0x7
  19 #define PUNIT_SEMAPHORE_CHT     0x10e
  20 #define PUNIT_SEMAPHORE_BIT     BIT(0)
  21 #define PUNIT_SEMAPHORE_ACQUIRE BIT(1)
  22
  23 static unsigned long acquired;
  24
  25 static u32 get_sem_addr(struct dw_i2c_dev *dev)
  26 {
  27         if (dev->flags & MODEL_CHERRYTRAIL)
  28                 return PUNIT_SEMAPHORE_CHT;
  29         else
  30                 return PUNIT_SEMAPHORE;
  31 }
  32
  33 static int get_sem(struct dw_i2c_dev *dev, u32 *sem)
  34 {
  35         u32 addr = get_sem_addr(dev);
  36         u32 data;
  37         int ret;
  38
  39         ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &data);
  40         if (ret) {
  41                 dev_err(dev->dev, "iosf failed to read punit semaphore\n");
  42                 return ret;
  43         }
  44
  45         *sem = data & PUNIT_SEMAPHORE_BIT;
  46
  47         return 0;
  48 }
  49
  50 static void reset_semaphore(struct dw_i2c_dev *dev)
  51 {
  52         if (iosf_mbi_modify(BT_MBI_UNIT_PMC, MBI_REG_READ, get_sem_addr(dev),
  53                             0, PUNIT_SEMAPHORE_BIT))
  54                 dev_err(dev->dev, "iosf failed to reset punit semaphore during write\n");
  55
  56         pm_qos_update_request(&dev->pm_qos, PM_QOS_DEFAULT_VALUE);
  57
  58         iosf_mbi_call_pmic_bus_access_notifier_chain(MBI_PMIC_BUS_ACCESS_END,
  59                                                      NULL);
  60         iosf_mbi_punit_release();
  61 }
  62
  63 static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
  64 {
  65         u32 addr;
  66         u32 sem = PUNIT_SEMAPHORE_ACQUIRE;
  67         int ret;
  68         unsigned long start, end;
  69
  70         might_sleep();
  71
  72         if (!dev || !dev->dev)
  73                 return -ENODEV;
  74
  75         if (!dev->release_lock)
  76                 return 0;
  77
  78         iosf_mbi_punit_acquire();
  79         iosf_mbi_call_pmic_bus_access_notifier_chain(MBI_PMIC_BUS_ACCESS_BEGIN,
  80                                                      NULL);
  81
  82         /*
  83          * Disallow the CPU to enter C6 or C7 state, entering these states
  84          * requires the punit to talk to the pmic and if this happens while
  85          * we're holding the semaphore, the SoC hangs.
  86          */
  87         pm_qos_update_request(&dev->pm_qos, 0);
  88
  89         addr = get_sem_addr(dev);
  90
  91         /* host driver writes to side band semaphore register */
  92         ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, addr, sem);
  93         if (ret) {
  94                 dev_err(dev->dev, "iosf punit semaphore request failed\n");
  95                 goto out;
  96         }
  97
  98         /* host driver waits for bit 0 to be set in semaphore register */
  99         start = jiffies;
 100         end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
 101         do {
 102                 ret = get_sem(dev, &sem);
 103                 if (!ret && sem) {
 104                         acquired = jiffies;
 105                         dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
 106                                 jiffies_to_msecs(jiffies - start));
 107                         return 0;
 108                 }
 109
 110                 usleep_range(1000, 2000);
 111         } while (time_before(jiffies, end));
 112
 113         dev_err(dev->dev, "punit semaphore timed out, resetting\n");
 114 out:
 115         reset_semaphore(dev);
 116
 117         ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, addr, &sem);
 118         if (ret)
 119                 dev_err(dev->dev, "iosf failed to read punit semaphore\n");
 120         else
 121                 dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
 122
 123         WARN_ON(1);
 124
 125         return -ETIMEDOUT;
 126 }
 127
 128 static void baytrail_i2c_release(struct dw_i2c_dev *dev)
 129 {
 130         if (!dev || !dev->dev)
 131                 return;
 132
 133         if (!dev->acquire_lock)
 134                 return;
 135
 136         reset_semaphore(dev);
 137         dev_dbg(dev->dev, "punit semaphore held for %ums\n",
 138                 jiffies_to_msecs(jiffies - acquired));
 139 }
 140
 141 int i2c_dw_probe_lock_support(struct dw_i2c_dev *dev)
 142 {
 143         acpi_status status;
 144         unsigned long long shared_host = 0;
 145         acpi_handle handle;
 146
 147         if (!dev || !dev->dev)
 148                 return 0;
 149
 150         handle = ACPI_HANDLE(dev->dev);
 151         if (!handle)
 152                 return 0;
 153
 154         status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
 155         if (ACPI_FAILURE(status))
 156                 return 0;
 157
 158         if (!shared_host)
 159                 return 0;
 160
 161         if (!iosf_mbi_available())
 162                 return -EPROBE_DEFER;
 163
 164         dev_info(dev->dev, "I2C bus managed by PUNIT\n");
 165         dev->acquire_lock = baytrail_i2c_acquire;
 166         dev->release_lock = baytrail_i2c_release;
 167         dev->pm_disabled = true;
 168
 169         pm_qos_add_request(&dev->pm_qos, PM_QOS_CPU_DMA_LATENCY,
 170                            PM_QOS_DEFAULT_VALUE);
 171
 172         return 0;
 173 }
 174
 175 void i2c_dw_remove_lock_support(struct dw_i2c_dev *dev)
 176 {
 177         if (dev->acquire_lock)
 178                 pm_qos_remove_request(&dev->pm_qos);
 179 }