drivers/hwspinlock/u8500_hsem.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * u8500 HWSEM driver
   4  *
   5  * Copyright (C) 2010-2011 ST-Ericsson
   6  *
   7  * Implements u8500 semaphore handling for protocol 1, no interrupts.
   8  *
   9  * Author: Mathieu Poirier <mathieu.poirier@linaro.org>
  10  * Heavily borrowed from the work of :
  11  *   Simon Que <sque@ti.com>
  12  *   Hari Kanigeri <h-kanigeri2@ti.com>
  13  *   Ohad Ben-Cohen <ohad@wizery.com>
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/delay.h>
  18 #include <linux/io.h>
  19 #include <linux/slab.h>
  20 #include <linux/spinlock.h>
  21 #include <linux/hwspinlock.h>
  22 #include <linux/platform_device.h>
  23
  24 #include "hwspinlock_internal.h"
  25
  26 /*
  27  * Implementation of STE's HSem protocol 1 without interrutps.
  28  * The only masterID we allow is '0x01' to force people to use
  29  * HSems for synchronisation between processors rather than processes
  30  * on the ARM core.
  31  */
  32
  33 #define U8500_MAX_SEMAPHORE             32      /* a total of 32 semaphore */
  34 #define RESET_SEMAPHORE                 (0)     /* free */
  35
  36 /*
  37  * CPU ID for master running u8500 kernel.
  38  * Hswpinlocks should only be used to synchonise operations
  39  * between the Cortex A9 core and the other CPUs.  Hence
  40  * forcing the masterID to a preset value.
  41  */
  42 #define HSEM_MASTER_ID                  0x01
  43
  44 #define HSEM_REGISTER_OFFSET            0x08
  45
  46 #define HSEM_CTRL_REG                   0x00
  47 #define HSEM_ICRALL                     0x90
  48 #define HSEM_PROTOCOL_1                 0x01
  49
  50 static int u8500_hsem_trylock(struct hwspinlock *lock)
  51 {
  52         void __iomem *lock_addr = lock->priv;
  53
  54         writel(HSEM_MASTER_ID, lock_addr);
  55
  56         /* get only first 4 bit and compare to masterID.
  57          * if equal, we have the semaphore, otherwise
  58          * someone else has it.
  59          */
  60         return (HSEM_MASTER_ID == (0x0F & readl(lock_addr)));
  61 }
  62
  63 static void u8500_hsem_unlock(struct hwspinlock *lock)
  64 {
  65         void __iomem *lock_addr = lock->priv;
  66
  67         /* release the lock by writing 0 to it */
  68         writel(RESET_SEMAPHORE, lock_addr);
  69 }
  70
  71 /*
  72  * u8500: what value is recommended here ?
  73  */
  74 static void u8500_hsem_relax(struct hwspinlock *lock)
  75 {
  76         ndelay(50);
  77 }
  78
  79 static const struct hwspinlock_ops u8500_hwspinlock_ops = {
  80         .trylock        = u8500_hsem_trylock,
  81         .unlock         = u8500_hsem_unlock,
  82         .relax          = u8500_hsem_relax,
  83 };
  84
  85 static int u8500_hsem_probe(struct platform_device *pdev)
  86 {
  87         struct hwspinlock_pdata *pdata = pdev->dev.platform_data;
  88         struct hwspinlock_device *bank;
  89         struct hwspinlock *hwlock;
  90         void __iomem *io_base;
  91         int i, num_locks = U8500_MAX_SEMAPHORE;
  92         ulong val;
  93
  94         if (!pdata)
  95                 return -ENODEV;
  96
  97         io_base = devm_platform_ioremap_resource(pdev, 0);
  98         if (IS_ERR(io_base))
  99                 return PTR_ERR(io_base);
 100
 101         /* make sure protocol 1 is selected */
 102         val = readl(io_base + HSEM_CTRL_REG);
 103         writel((val & ~HSEM_PROTOCOL_1), io_base + HSEM_CTRL_REG);
 104
 105         /* clear all interrupts */
 106         writel(0xFFFF, io_base + HSEM_ICRALL);
 107
 108         bank = devm_kzalloc(&pdev->dev, struct_size(bank, lock, num_locks),
 109                             GFP_KERNEL);
 110         if (!bank)
 111                 return -ENOMEM;
 112
 113         platform_set_drvdata(pdev, bank);
 114
 115         for (i = 0, hwlock = &bank->lock[0]; i < num_locks; i++, hwlock++)
 116                 hwlock->priv = io_base + HSEM_REGISTER_OFFSET + sizeof(u32) * i;
 117
 118         return devm_hwspin_lock_register(&pdev->dev, bank,
 119                                          &u8500_hwspinlock_ops,
 120                                          pdata->base_id, num_locks);
 121 }
 122
 123 static void u8500_hsem_remove(struct platform_device *pdev)
 124 {
 125         struct hwspinlock_device *bank = platform_get_drvdata(pdev);
 126         void __iomem *io_base = bank->lock[0].priv - HSEM_REGISTER_OFFSET;
 127
 128         /* clear all interrupts */
 129         writel(0xFFFF, io_base + HSEM_ICRALL);
 130 }
 131
 132 static struct platform_driver u8500_hsem_driver = {
 133         .probe          = u8500_hsem_probe,
 134         .remove_new     = u8500_hsem_remove,
 135         .driver         = {
 136                 .name   = "u8500_hsem",
 137         },
 138 };
 139
 140 static int __init u8500_hsem_init(void)
 141 {
 142         return platform_driver_register(&u8500_hsem_driver);
 143 }
 144 /* board init code might need to reserve hwspinlocks for predefined purposes */
 145 postcore_initcall(u8500_hsem_init);
 146
 147 static void __exit u8500_hsem_exit(void)
 148 {
 149         platform_driver_unregister(&u8500_hsem_driver);
 150 }
 151 module_exit(u8500_hsem_exit);
 152
 153 MODULE_LICENSE("GPL v2");
 154 MODULE_DESCRIPTION("Hardware Spinlock driver for u8500");
 155 MODULE_AUTHOR("Mathieu Poirier <mathieu.poirier@linaro.org>");