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Shiraz Hashimb53bc282012-11-16 10:45:25 +05301/*
2 * SPEAr platform SPI chipselect abstraction over gpiolib
3 *
4 * Copyright (C) 2012 ST Microelectronics
5 * Shiraz Hashim <shiraz.hashim@st.com>
6 *
7 * This file is licensed under the terms of the GNU General Public
8 * License version 2. This program is licensed "as is" without any
9 * warranty of any kind, whether express or implied.
10 */
11
12#include <linux/err.h>
13#include <linux/gpio.h>
14#include <linux/io.h>
15#include <linux/module.h>
16#include <linux/of.h>
17#include <linux/platform_device.h>
18#include <linux/types.h>
19
20/* maximum chipselects */
21#define NUM_OF_GPIO 4
22
23/*
24 * Provision is available on some SPEAr SoCs to control ARM PL022 spi cs
25 * through system registers. This register lies outside spi (pl022)
26 * address space into system registers.
27 *
28 * It provides control for spi chip select lines so that any chipselect
29 * (out of 4 possible chipselects in pl022) can be made low to select
30 * the particular slave.
31 */
32
33/**
34 * struct spear_spics - represents spi chip select control
35 * @base: base address
36 * @perip_cfg: configuration register
37 * @sw_enable_bit: bit to enable s/w control over chipselects
38 * @cs_value_bit: bit to program high or low chipselect
39 * @cs_enable_mask: mask to select bits required to select chipselect
40 * @cs_enable_shift: bit pos of cs_enable_mask
41 * @use_count: use count of a spi controller cs lines
42 * @last_off: stores last offset caller of set_value()
43 * @chip: gpio_chip abstraction
44 */
45struct spear_spics {
46 void __iomem *base;
47 u32 perip_cfg;
48 u32 sw_enable_bit;
49 u32 cs_value_bit;
50 u32 cs_enable_mask;
51 u32 cs_enable_shift;
52 unsigned long use_count;
53 int last_off;
54 struct gpio_chip chip;
55};
56
57/* gpio framework specific routines */
58static int spics_get_value(struct gpio_chip *chip, unsigned offset)
59{
60 return -ENXIO;
61}
62
63static void spics_set_value(struct gpio_chip *chip, unsigned offset, int value)
64{
65 struct spear_spics *spics = container_of(chip, struct spear_spics,
66 chip);
67 u32 tmp;
68
69 /* select chip select from register */
70 tmp = readl_relaxed(spics->base + spics->perip_cfg);
71 if (spics->last_off != offset) {
72 spics->last_off = offset;
73 tmp &= ~(spics->cs_enable_mask << spics->cs_enable_shift);
74 tmp |= offset << spics->cs_enable_shift;
75 }
76
77 /* toggle chip select line */
78 tmp &= ~(0x1 << spics->cs_value_bit);
79 tmp |= value << spics->cs_value_bit;
80 writel_relaxed(tmp, spics->base + spics->perip_cfg);
81}
82
83static int spics_direction_input(struct gpio_chip *chip, unsigned offset)
84{
85 return -ENXIO;
86}
87
88static int spics_direction_output(struct gpio_chip *chip, unsigned offset,
89 int value)
90{
91 spics_set_value(chip, offset, value);
92 return 0;
93}
94
95static int spics_request(struct gpio_chip *chip, unsigned offset)
96{
97 struct spear_spics *spics = container_of(chip, struct spear_spics,
98 chip);
99 u32 tmp;
100
101 if (!spics->use_count++) {
102 tmp = readl_relaxed(spics->base + spics->perip_cfg);
103 tmp |= 0x1 << spics->sw_enable_bit;
104 tmp |= 0x1 << spics->cs_value_bit;
105 writel_relaxed(tmp, spics->base + spics->perip_cfg);
106 }
107
108 return 0;
109}
110
111static void spics_free(struct gpio_chip *chip, unsigned offset)
112{
113 struct spear_spics *spics = container_of(chip, struct spear_spics,
114 chip);
115 u32 tmp;
116
117 if (!--spics->use_count) {
118 tmp = readl_relaxed(spics->base + spics->perip_cfg);
119 tmp &= ~(0x1 << spics->sw_enable_bit);
120 writel_relaxed(tmp, spics->base + spics->perip_cfg);
121 }
122}
123
124static int spics_gpio_probe(struct platform_device *pdev)
125{
126 struct device_node *np = pdev->dev.of_node;
127 struct spear_spics *spics;
128 struct resource *res;
129 int ret;
130
131 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
132 if (!res) {
133 dev_err(&pdev->dev, "invalid IORESOURCE_MEM\n");
134 return -EBUSY;
135 }
136
137 spics = devm_kzalloc(&pdev->dev, sizeof(*spics), GFP_KERNEL);
138 if (!spics) {
139 dev_err(&pdev->dev, "memory allocation fail\n");
140 return -ENOMEM;
141 }
142
Thierry Reding641d0342013-01-21 11:09:01 +0100143 spics->base = devm_ioremap_resource(&pdev->dev, res);
144 if (IS_ERR(spics->base))
145 return PTR_ERR(spics->base);
Shiraz Hashimb53bc282012-11-16 10:45:25 +0530146
147 if (of_property_read_u32(np, "st-spics,peripcfg-reg",
148 &spics->perip_cfg))
149 goto err_dt_data;
150 if (of_property_read_u32(np, "st-spics,sw-enable-bit",
151 &spics->sw_enable_bit))
152 goto err_dt_data;
153 if (of_property_read_u32(np, "st-spics,cs-value-bit",
154 &spics->cs_value_bit))
155 goto err_dt_data;
156 if (of_property_read_u32(np, "st-spics,cs-enable-mask",
157 &spics->cs_enable_mask))
158 goto err_dt_data;
159 if (of_property_read_u32(np, "st-spics,cs-enable-shift",
160 &spics->cs_enable_shift))
161 goto err_dt_data;
162
163 platform_set_drvdata(pdev, spics);
164
165 spics->chip.ngpio = NUM_OF_GPIO;
166 spics->chip.base = -1;
167 spics->chip.request = spics_request;
168 spics->chip.free = spics_free;
169 spics->chip.direction_input = spics_direction_input;
170 spics->chip.direction_output = spics_direction_output;
171 spics->chip.get = spics_get_value;
172 spics->chip.set = spics_set_value;
173 spics->chip.label = dev_name(&pdev->dev);
174 spics->chip.dev = &pdev->dev;
175 spics->chip.owner = THIS_MODULE;
176 spics->last_off = -1;
177
178 ret = gpiochip_add(&spics->chip);
179 if (ret) {
180 dev_err(&pdev->dev, "unable to add gpio chip\n");
181 return ret;
182 }
183
184 dev_info(&pdev->dev, "spear spics registered\n");
185 return 0;
186
187err_dt_data:
188 dev_err(&pdev->dev, "DT probe failed\n");
189 return -EINVAL;
190}
191
192static const struct of_device_id spics_gpio_of_match[] = {
193 { .compatible = "st,spear-spics-gpio" },
194 {}
195};
196MODULE_DEVICE_TABLE(of, spics_gpio_of_match);
197
198static struct platform_driver spics_gpio_driver = {
199 .probe = spics_gpio_probe,
200 .driver = {
201 .owner = THIS_MODULE,
202 .name = "spear-spics-gpio",
203 .of_match_table = spics_gpio_of_match,
204 },
205};
206
207static int __init spics_gpio_init(void)
208{
209 return platform_driver_register(&spics_gpio_driver);
210}
211subsys_initcall(spics_gpio_init);
212
213MODULE_AUTHOR("Shiraz Hashim <shiraz.hashim@st.com>");
214MODULE_DESCRIPTION("ST Microlectronics SPEAr SPI Chip Select Abstraction");
215MODULE_LICENSE("GPL");