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>");
156