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
 50static 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
 63static 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 */
 74static void u8500_hsem_relax(struct hwspinlock *lock)
 75{
 76	ndelay(50);
 77}
 78
 79static const struct hwspinlock_ops u8500_hwspinlock_ops = {
 80	.trylock	= u8500_hsem_trylock,
 81	.unlock		= u8500_hsem_unlock,
 82	.relax		= u8500_hsem_relax,
 83};
 84
 85static 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
123static int 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	return 0;
132}
133
134static struct platform_driver u8500_hsem_driver = {
135	.probe		= u8500_hsem_probe,
136	.remove		= u8500_hsem_remove,
137	.driver		= {
138		.name	= "u8500_hsem",
139	},
140};
141
142static int __init u8500_hsem_init(void)
143{
144	return platform_driver_register(&u8500_hsem_driver);
145}
146/* board init code might need to reserve hwspinlocks for predefined purposes */
147postcore_initcall(u8500_hsem_init);
148
149static void __exit u8500_hsem_exit(void)
150{
151	platform_driver_unregister(&u8500_hsem_driver);
152}
153module_exit(u8500_hsem_exit);
154
155MODULE_LICENSE("GPL v2");
156MODULE_DESCRIPTION("Hardware Spinlock driver for u8500");
157MODULE_AUTHOR("Mathieu Poirier <mathieu.poirier@linaro.org>");