xref: /openbmc/linux/drivers/gpio/gpio-mm-lantiq.c (revision 12eb4683)
1 /*
2  *  This program is free software; you can redistribute it and/or modify it
3  *  under the terms of the GNU General Public License version 2 as published
4  *  by the Free Software Foundation.
5  *
6  *  Copyright (C) 2012 John Crispin <blogic@openwrt.org>
7  */
8 
9 #include <linux/init.h>
10 #include <linux/module.h>
11 #include <linux/types.h>
12 #include <linux/platform_device.h>
13 #include <linux/mutex.h>
14 #include <linux/gpio.h>
15 #include <linux/of.h>
16 #include <linux/of_gpio.h>
17 #include <linux/io.h>
18 #include <linux/slab.h>
19 
20 #include <lantiq_soc.h>
21 
22 /*
23  * By attaching hardware latches to the EBU it is possible to create output
24  * only gpios. This driver configures a special memory address, which when
25  * written to outputs 16 bit to the latches.
26  */
27 
28 #define LTQ_EBU_BUSCON	0x1e7ff		/* 16 bit access, slowest timing */
29 #define LTQ_EBU_WP	0x80000000	/* write protect bit */
30 
31 struct ltq_mm {
32 	struct of_mm_gpio_chip mmchip;
33 	u16 shadow;	/* shadow the latches state */
34 };
35 
36 /**
37  * ltq_mm_apply() - write the shadow value to the ebu address.
38  * @chip:     Pointer to our private data structure.
39  *
40  * Write the shadow value to the EBU to set the gpios. We need to set the
41  * global EBU lock to make sure that PCI/MTD dont break.
42  */
43 static void ltq_mm_apply(struct ltq_mm *chip)
44 {
45 	unsigned long flags;
46 
47 	spin_lock_irqsave(&ebu_lock, flags);
48 	ltq_ebu_w32(LTQ_EBU_BUSCON, LTQ_EBU_BUSCON1);
49 	__raw_writew(chip->shadow, chip->mmchip.regs);
50 	ltq_ebu_w32(LTQ_EBU_BUSCON | LTQ_EBU_WP, LTQ_EBU_BUSCON1);
51 	spin_unlock_irqrestore(&ebu_lock, flags);
52 }
53 
54 /**
55  * ltq_mm_set() - gpio_chip->set - set gpios.
56  * @gc:     Pointer to gpio_chip device structure.
57  * @gpio:   GPIO signal number.
58  * @val:    Value to be written to specified signal.
59  *
60  * Set the shadow value and call ltq_mm_apply.
61  */
62 static void ltq_mm_set(struct gpio_chip *gc, unsigned offset, int value)
63 {
64 	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
65 	struct ltq_mm *chip =
66 		container_of(mm_gc, struct ltq_mm, mmchip);
67 
68 	if (value)
69 		chip->shadow |= (1 << offset);
70 	else
71 		chip->shadow &= ~(1 << offset);
72 	ltq_mm_apply(chip);
73 }
74 
75 /**
76  * ltq_mm_dir_out() - gpio_chip->dir_out - set gpio direction.
77  * @gc:     Pointer to gpio_chip device structure.
78  * @gpio:   GPIO signal number.
79  * @val:    Value to be written to specified signal.
80  *
81  * Same as ltq_mm_set, always returns 0.
82  */
83 static int ltq_mm_dir_out(struct gpio_chip *gc, unsigned offset, int value)
84 {
85 	ltq_mm_set(gc, offset, value);
86 
87 	return 0;
88 }
89 
90 /**
91  * ltq_mm_save_regs() - Set initial values of GPIO pins
92  * @mm_gc: pointer to memory mapped GPIO chip structure
93  */
94 static void ltq_mm_save_regs(struct of_mm_gpio_chip *mm_gc)
95 {
96 	struct ltq_mm *chip =
97 		container_of(mm_gc, struct ltq_mm, mmchip);
98 
99 	/* tell the ebu controller which memory address we will be using */
100 	ltq_ebu_w32(CPHYSADDR(chip->mmchip.regs) | 0x1, LTQ_EBU_ADDRSEL1);
101 
102 	ltq_mm_apply(chip);
103 }
104 
105 static int ltq_mm_probe(struct platform_device *pdev)
106 {
107 	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
108 	struct ltq_mm *chip;
109 	const __be32 *shadow;
110 	int ret = 0;
111 
112 	if (!res) {
113 		dev_err(&pdev->dev, "failed to get memory resource\n");
114 		return -ENOENT;
115 	}
116 
117 	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
118 	if (!chip)
119 		return -ENOMEM;
120 
121 	chip->mmchip.gc.ngpio = 16;
122 	chip->mmchip.gc.label = "gpio-mm-ltq";
123 	chip->mmchip.gc.direction_output = ltq_mm_dir_out;
124 	chip->mmchip.gc.set = ltq_mm_set;
125 	chip->mmchip.save_regs = ltq_mm_save_regs;
126 
127 	/* store the shadow value if one was passed by the devicetree */
128 	shadow = of_get_property(pdev->dev.of_node, "lantiq,shadow", NULL);
129 	if (shadow)
130 		chip->shadow = be32_to_cpu(*shadow);
131 
132 	ret = of_mm_gpiochip_add(pdev->dev.of_node, &chip->mmchip);
133 	if (ret)
134 		kfree(chip);
135 	return ret;
136 }
137 
138 static const struct of_device_id ltq_mm_match[] = {
139 	{ .compatible = "lantiq,gpio-mm" },
140 	{},
141 };
142 MODULE_DEVICE_TABLE(of, ltq_mm_match);
143 
144 static struct platform_driver ltq_mm_driver = {
145 	.probe = ltq_mm_probe,
146 	.driver = {
147 		.name = "gpio-mm-ltq",
148 		.owner = THIS_MODULE,
149 		.of_match_table = ltq_mm_match,
150 	},
151 };
152 
153 static int __init ltq_mm_init(void)
154 {
155 	return platform_driver_register(&ltq_mm_driver);
156 }
157 
158 subsys_initcall(ltq_mm_init);
159