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 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
132static 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
140static 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 */
145postcore_initcall(u8500_hsem_init);
146
147static void __exit u8500_hsem_exit(void)
148{
149	platform_driver_unregister(&u8500_hsem_driver);
150}
151module_exit(u8500_hsem_exit);
152
153MODULE_LICENSE("GPL v2");
154MODULE_DESCRIPTION("Hardware Spinlock driver for u8500");
155MODULE_AUTHOR("Mathieu Poirier <mathieu.poirier@linaro.org>");
156