drivers/hwspinlock/u8500_hsem.c

   1 /*
   2  * u8500 HWSEM driver
   3  *
   4  * Copyright (C) 2010-2011 ST-Ericsson
   5  *
   6  * Implements u8500 semaphore handling for protocol 1, no interrupts.
   7  *
   8  * Author: Mathieu Poirier <mathieu.poirier@linaro.org>
   9  * Heavily borrowed from the work of :
  10  *   Simon Que <sque@ti.com>
  11  *   Hari Kanigeri <h-kanigeri2@ti.com>
  12  *   Ohad Ben-Cohen <ohad@wizery.com>
  13  *
  14  * This program is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU General Public License
  16  * version 2 as published by the Free Software Foundation.
  17  *
  18  * This program is distributed in the hope that it will be useful, but
  19  * WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  21  * General Public License for more details.
  22  */
  23
  24 #include <linux/module.h>
  25 #include <linux/delay.h>
  26 #include <linux/io.h>
  27 #include <linux/pm_runtime.h>
  28 #include <linux/slab.h>
  29 #include <linux/spinlock.h>
  30 #include <linux/hwspinlock.h>
  31 #include <linux/platform_device.h>
  32
  33 #include "hwspinlock_internal.h"
  34
  35 /*
  36  * Implementation of STE's HSem protocol 1 without interrutps.
  37  * The only masterID we allow is '0x01' to force people to use
  38  * HSems for synchronisation between processors rather than processes
  39  * on the ARM core.
  40  */
  41
  42 #define U8500_MAX_SEMAPHORE             32      /* a total of 32 semaphore */
  43 #define RESET_SEMAPHORE                 (0)     /* free */
  44
  45 /*
  46  * CPU ID for master running u8500 kernel.
  47  * Hswpinlocks should only be used to synchonise operations
  48  * between the Cortex A9 core and the other CPUs.  Hence
  49  * forcing the masterID to a preset value.
  50  */
  51 #define HSEM_MASTER_ID                  0x01
  52
  53 #define HSEM_REGISTER_OFFSET            0x08
  54
  55 #define HSEM_CTRL_REG                   0x00
  56 #define HSEM_ICRALL                     0x90
  57 #define HSEM_PROTOCOL_1                 0x01
  58
  59 static int u8500_hsem_trylock(struct hwspinlock *lock)
  60 {
  61         void __iomem *lock_addr = lock->priv;
  62
  63         writel(HSEM_MASTER_ID, lock_addr);
  64
  65         /* get only first 4 bit and compare to masterID.
  66          * if equal, we have the semaphore, otherwise
  67          * someone else has it.
  68          */
  69         return (HSEM_MASTER_ID == (0x0F & readl(lock_addr)));
  70 }
  71
  72 static void u8500_hsem_unlock(struct hwspinlock *lock)
  73 {
  74         void __iomem *lock_addr = lock->priv;
  75
  76         /* release the lock by writing 0 to it */
  77         writel(RESET_SEMAPHORE, lock_addr);
  78 }
  79
  80 /*
  81  * u8500: what value is recommended here ?
  82  */
  83 static void u8500_hsem_relax(struct hwspinlock *lock)
  84 {
  85         ndelay(50);
  86 }
  87
  88 static const struct hwspinlock_ops u8500_hwspinlock_ops = {
  89         .trylock        = u8500_hsem_trylock,
  90         .unlock         = u8500_hsem_unlock,
  91         .relax          = u8500_hsem_relax,
  92 };
  93
  94 static int __devinit u8500_hsem_probe(struct platform_device *pdev)
  95 {
  96         struct hwspinlock_pdata *pdata = pdev->dev.platform_data;
  97         struct hwspinlock_device *bank;
  98         struct hwspinlock *hwlock;
  99         struct resource *res;
 100         void __iomem *io_base;
 101         int i, ret, num_locks = U8500_MAX_SEMAPHORE;
 102         ulong val;
 103
 104         if (!pdata)
 105                 return -ENODEV;
 106
 107         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 108         if (!res)
 109                 return -ENODEV;
 110
 111         io_base = ioremap(res->start, resource_size(res));
 112         if (!io_base)
 113                 return -ENOMEM;
 114
 115         /* make sure protocol 1 is selected */
 116         val = readl(io_base + HSEM_CTRL_REG);
 117         writel((val & ~HSEM_PROTOCOL_1), io_base + HSEM_CTRL_REG);
 118
 119         /* clear all interrupts */
 120         writel(0xFFFF, io_base + HSEM_ICRALL);
 121
 122         bank = kzalloc(sizeof(*bank) + num_locks * sizeof(*hwlock), GFP_KERNEL);
 123         if (!bank) {
 124                 ret = -ENOMEM;
 125                 goto iounmap_base;
 126         }
 127
 128         platform_set_drvdata(pdev, bank);
 129
 130         for (i = 0, hwlock = &bank->lock[0]; i < num_locks; i++, hwlock++)
 131                 hwlock->priv = io_base + HSEM_REGISTER_OFFSET + sizeof(u32) * i;
 132
 133         /* no pm needed for HSem but required to comply with hwspilock core */
 134         pm_runtime_enable(&pdev->dev);
 135
 136         ret = hwspin_lock_register(bank, &pdev->dev, &u8500_hwspinlock_ops,
 137                                                 pdata->base_id, num_locks);
 138         if (ret)
 139                 goto reg_fail;
 140
 141         return 0;
 142
 143 reg_fail:
 144         pm_runtime_disable(&pdev->dev);
 145         kfree(bank);
 146 iounmap_base:
 147         iounmap(io_base);
 148         return ret;
 149 }
 150
 151 static int __devexit u8500_hsem_remove(struct platform_device *pdev)
 152 {
 153         struct hwspinlock_device *bank = platform_get_drvdata(pdev);
 154         void __iomem *io_base = bank->lock[0].priv - HSEM_REGISTER_OFFSET;
 155         int ret;
 156
 157         /* clear all interrupts */
 158         writel(0xFFFF, io_base + HSEM_ICRALL);
 159
 160         ret = hwspin_lock_unregister(bank);
 161         if (ret) {
 162                 dev_err(&pdev->dev, "%s failed: %d\n", __func__, ret);
 163                 return ret;
 164         }
 165
 166         pm_runtime_disable(&pdev->dev);
 167         iounmap(io_base);
 168         kfree(bank);
 169
 170         return 0;
 171 }
 172
 173 static struct platform_driver u8500_hsem_driver = {
 174         .probe          = u8500_hsem_probe,
 175         .remove         = __devexit_p(u8500_hsem_remove),
 176         .driver         = {
 177                 .name   = "u8500_hsem",
 178                 .owner  = THIS_MODULE,
 179         },
 180 };
 181
 182 static int __init u8500_hsem_init(void)
 183 {
 184         return platform_driver_register(&u8500_hsem_driver);
 185 }
 186 /* board init code might need to reserve hwspinlocks for predefined purposes */
 187 postcore_initcall(u8500_hsem_init);
 188
 189 static void __exit u8500_hsem_exit(void)
 190 {
 191         platform_driver_unregister(&u8500_hsem_driver);
 192 }
 193 module_exit(u8500_hsem_exit);
 194
 195 MODULE_LICENSE("GPL v2");
 196 MODULE_DESCRIPTION("Hardware Spinlock driver for u8500");
 197 MODULE_AUTHOR("Mathieu Poirier <mathieu.poirier@linaro.org>");