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c942fddf | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
7ecbfff6 SI |
2 | /* |
3 | * SPI master driver for ICP DAS LP-8841 RTC | |
4 | * | |
5 | * Copyright (C) 2016 Sergei Ianovich | |
6 | * | |
7 | * based on | |
8 | * | |
9 | * Dallas DS1302 RTC Support | |
10 | * Copyright (C) 2002 David McCullough | |
11 | * Copyright (C) 2003 - 2007 Paul Mundt | |
7ecbfff6 SI |
12 | */ |
13 | #include <linux/delay.h> | |
14 | #include <linux/kernel.h> | |
15 | #include <linux/module.h> | |
16 | #include <linux/platform_device.h> | |
17 | #include <linux/of.h> | |
18 | #include <linux/of_device.h> | |
19 | #include <linux/spi/spi.h> | |
20 | ||
21 | #define DRIVER_NAME "spi_lp8841_rtc" | |
22 | ||
23 | #define SPI_LP8841_RTC_CE 0x01 | |
24 | #define SPI_LP8841_RTC_CLK 0x02 | |
25 | #define SPI_LP8841_RTC_nWE 0x04 | |
26 | #define SPI_LP8841_RTC_MOSI 0x08 | |
27 | #define SPI_LP8841_RTC_MISO 0x01 | |
28 | ||
29 | /* | |
30 | * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI | |
31 | * GPIO driver, this SPI driver can be replaced by a simple GPIO driver | |
32 | * providing 3 GPIO pins. | |
33 | */ | |
34 | ||
35 | struct spi_lp8841_rtc { | |
36 | void *iomem; | |
37 | unsigned long state; | |
38 | }; | |
39 | ||
40 | static inline void | |
41 | setsck(struct spi_lp8841_rtc *data, int is_on) | |
42 | { | |
43 | if (is_on) | |
44 | data->state |= SPI_LP8841_RTC_CLK; | |
45 | else | |
46 | data->state &= ~SPI_LP8841_RTC_CLK; | |
47 | writeb(data->state, data->iomem); | |
48 | } | |
49 | ||
50 | static inline void | |
51 | setmosi(struct spi_lp8841_rtc *data, int is_on) | |
52 | { | |
53 | if (is_on) | |
54 | data->state |= SPI_LP8841_RTC_MOSI; | |
55 | else | |
56 | data->state &= ~SPI_LP8841_RTC_MOSI; | |
57 | writeb(data->state, data->iomem); | |
58 | } | |
59 | ||
60 | static inline int | |
61 | getmiso(struct spi_lp8841_rtc *data) | |
62 | { | |
63 | return ioread8(data->iomem) & SPI_LP8841_RTC_MISO; | |
64 | } | |
65 | ||
66 | static inline u32 | |
67 | bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data, | |
68 | unsigned usecs, unsigned cpol, unsigned flags, | |
69 | u32 word, u8 bits) | |
70 | { | |
71 | /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ | |
72 | ||
73 | u32 shift = 32 - bits; | |
74 | /* clock starts at inactive polarity */ | |
75 | for (; likely(bits); bits--) { | |
76 | ||
77 | /* setup LSB (to slave) on leading edge */ | |
78 | if ((flags & SPI_MASTER_NO_TX) == 0) | |
79 | setmosi(data, (word & 1)); | |
80 | ||
81 | usleep_range(usecs, usecs + 1); /* T(setup) */ | |
82 | ||
83 | /* sample LSB (from slave) on trailing edge */ | |
84 | word >>= 1; | |
85 | if ((flags & SPI_MASTER_NO_RX) == 0) | |
86 | word |= (getmiso(data) << 31); | |
87 | ||
88 | setsck(data, !cpol); | |
89 | usleep_range(usecs, usecs + 1); | |
90 | ||
91 | setsck(data, cpol); | |
92 | } | |
93 | ||
94 | word >>= shift; | |
95 | return word; | |
96 | } | |
97 | ||
98 | static int | |
99 | spi_lp8841_rtc_transfer_one(struct spi_master *master, | |
100 | struct spi_device *spi, | |
101 | struct spi_transfer *t) | |
102 | { | |
103 | struct spi_lp8841_rtc *data = spi_master_get_devdata(master); | |
104 | unsigned count = t->len; | |
105 | const u8 *tx = t->tx_buf; | |
106 | u8 *rx = t->rx_buf; | |
107 | u8 word = 0; | |
108 | int ret = 0; | |
109 | ||
110 | if (tx) { | |
111 | data->state &= ~SPI_LP8841_RTC_nWE; | |
112 | writeb(data->state, data->iomem); | |
113 | while (likely(count > 0)) { | |
114 | word = *tx++; | |
115 | bitbang_txrx_be_cpha0_lsb(data, 1, 0, | |
116 | SPI_MASTER_NO_RX, word, 8); | |
117 | count--; | |
118 | } | |
119 | } else if (rx) { | |
120 | data->state |= SPI_LP8841_RTC_nWE; | |
121 | writeb(data->state, data->iomem); | |
122 | while (likely(count > 0)) { | |
123 | word = bitbang_txrx_be_cpha0_lsb(data, 1, 0, | |
124 | SPI_MASTER_NO_TX, word, 8); | |
125 | *rx++ = word; | |
126 | count--; | |
127 | } | |
128 | } else { | |
129 | ret = -EINVAL; | |
130 | } | |
131 | ||
132 | spi_finalize_current_transfer(master); | |
133 | ||
134 | return ret; | |
135 | } | |
136 | ||
137 | static void | |
138 | spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable) | |
139 | { | |
140 | struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master); | |
141 | ||
142 | data->state = 0; | |
143 | writeb(data->state, data->iomem); | |
144 | if (enable) { | |
145 | usleep_range(4, 5); | |
146 | data->state |= SPI_LP8841_RTC_CE; | |
147 | writeb(data->state, data->iomem); | |
148 | usleep_range(4, 5); | |
149 | } | |
150 | } | |
151 | ||
152 | static int | |
153 | spi_lp8841_rtc_setup(struct spi_device *spi) | |
154 | { | |
155 | if ((spi->mode & SPI_CS_HIGH) == 0) { | |
156 | dev_err(&spi->dev, "unsupported active low chip select\n"); | |
157 | return -EINVAL; | |
158 | } | |
159 | ||
160 | if ((spi->mode & SPI_LSB_FIRST) == 0) { | |
161 | dev_err(&spi->dev, "unsupported MSB first mode\n"); | |
162 | return -EINVAL; | |
163 | } | |
164 | ||
165 | if ((spi->mode & SPI_3WIRE) == 0) { | |
166 | dev_err(&spi->dev, "unsupported wiring. 3 wires required\n"); | |
167 | return -EINVAL; | |
168 | } | |
169 | ||
170 | return 0; | |
171 | } | |
172 | ||
173 | #ifdef CONFIG_OF | |
174 | static const struct of_device_id spi_lp8841_rtc_dt_ids[] = { | |
175 | { .compatible = "icpdas,lp8841-spi-rtc" }, | |
176 | { } | |
177 | }; | |
178 | ||
179 | MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids); | |
180 | #endif | |
181 | ||
182 | static int | |
183 | spi_lp8841_rtc_probe(struct platform_device *pdev) | |
184 | { | |
185 | int ret; | |
186 | struct spi_master *master; | |
187 | struct spi_lp8841_rtc *data; | |
7ecbfff6 SI |
188 | |
189 | master = spi_alloc_master(&pdev->dev, sizeof(*data)); | |
190 | if (!master) | |
191 | return -ENOMEM; | |
192 | platform_set_drvdata(pdev, master); | |
193 | ||
194 | master->flags = SPI_MASTER_HALF_DUPLEX; | |
195 | master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST; | |
196 | ||
197 | master->bus_num = pdev->id; | |
198 | master->num_chipselect = 1; | |
199 | master->setup = spi_lp8841_rtc_setup; | |
200 | master->set_cs = spi_lp8841_rtc_set_cs; | |
201 | master->transfer_one = spi_lp8841_rtc_transfer_one; | |
202 | master->bits_per_word_mask = SPI_BPW_MASK(8); | |
203 | #ifdef CONFIG_OF | |
204 | master->dev.of_node = pdev->dev.of_node; | |
205 | #endif | |
206 | ||
207 | data = spi_master_get_devdata(master); | |
208 | ||
7d2600b9 | 209 | data->iomem = devm_platform_ioremap_resource(pdev, 0); |
14a20428 AB |
210 | ret = PTR_ERR_OR_ZERO(data->iomem); |
211 | if (ret) { | |
7ecbfff6 SI |
212 | dev_err(&pdev->dev, "failed to get IO address\n"); |
213 | goto err_put_master; | |
214 | } | |
215 | ||
216 | /* register with the SPI framework */ | |
217 | ret = devm_spi_register_master(&pdev->dev, master); | |
218 | if (ret) { | |
219 | dev_err(&pdev->dev, "cannot register spi master\n"); | |
220 | goto err_put_master; | |
221 | } | |
222 | ||
223 | return ret; | |
224 | ||
225 | ||
226 | err_put_master: | |
227 | spi_master_put(master); | |
228 | ||
229 | return ret; | |
230 | } | |
231 | ||
232 | MODULE_ALIAS("platform:" DRIVER_NAME); | |
233 | ||
234 | static struct platform_driver spi_lp8841_rtc_driver = { | |
235 | .driver = { | |
236 | .name = DRIVER_NAME, | |
237 | .of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids), | |
238 | }, | |
239 | .probe = spi_lp8841_rtc_probe, | |
240 | }; | |
241 | module_platform_driver(spi_lp8841_rtc_driver); | |
242 | ||
243 | MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC"); | |
244 | MODULE_AUTHOR("Sergei Ianovich"); | |
245 | MODULE_LICENSE("GPL"); |