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7ecbfff6 SI |
1 | /* |
2 | * SPI master driver for ICP DAS LP-8841 RTC | |
3 | * | |
4 | * Copyright (C) 2016 Sergei Ianovich | |
5 | * | |
6 | * based on | |
7 | * | |
8 | * Dallas DS1302 RTC Support | |
9 | * Copyright (C) 2002 David McCullough | |
10 | * Copyright (C) 2003 - 2007 Paul Mundt | |
11 | * | |
12 | * This program is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU General Public License as published by | |
14 | * the Free Software Foundation; either version 2 of the License, or | |
15 | * (at your option) any later version. | |
16 | * | |
17 | * This program is distributed in the hope that it will be useful, | |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU General Public License for more details. | |
21 | */ | |
22 | #include <linux/delay.h> | |
23 | #include <linux/kernel.h> | |
24 | #include <linux/module.h> | |
25 | #include <linux/platform_device.h> | |
26 | #include <linux/of.h> | |
27 | #include <linux/of_device.h> | |
28 | #include <linux/spi/spi.h> | |
29 | ||
30 | #define DRIVER_NAME "spi_lp8841_rtc" | |
31 | ||
32 | #define SPI_LP8841_RTC_CE 0x01 | |
33 | #define SPI_LP8841_RTC_CLK 0x02 | |
34 | #define SPI_LP8841_RTC_nWE 0x04 | |
35 | #define SPI_LP8841_RTC_MOSI 0x08 | |
36 | #define SPI_LP8841_RTC_MISO 0x01 | |
37 | ||
38 | /* | |
39 | * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI | |
40 | * GPIO driver, this SPI driver can be replaced by a simple GPIO driver | |
41 | * providing 3 GPIO pins. | |
42 | */ | |
43 | ||
44 | struct spi_lp8841_rtc { | |
45 | void *iomem; | |
46 | unsigned long state; | |
47 | }; | |
48 | ||
49 | static inline void | |
50 | setsck(struct spi_lp8841_rtc *data, int is_on) | |
51 | { | |
52 | if (is_on) | |
53 | data->state |= SPI_LP8841_RTC_CLK; | |
54 | else | |
55 | data->state &= ~SPI_LP8841_RTC_CLK; | |
56 | writeb(data->state, data->iomem); | |
57 | } | |
58 | ||
59 | static inline void | |
60 | setmosi(struct spi_lp8841_rtc *data, int is_on) | |
61 | { | |
62 | if (is_on) | |
63 | data->state |= SPI_LP8841_RTC_MOSI; | |
64 | else | |
65 | data->state &= ~SPI_LP8841_RTC_MOSI; | |
66 | writeb(data->state, data->iomem); | |
67 | } | |
68 | ||
69 | static inline int | |
70 | getmiso(struct spi_lp8841_rtc *data) | |
71 | { | |
72 | return ioread8(data->iomem) & SPI_LP8841_RTC_MISO; | |
73 | } | |
74 | ||
75 | static inline u32 | |
76 | bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data, | |
77 | unsigned usecs, unsigned cpol, unsigned flags, | |
78 | u32 word, u8 bits) | |
79 | { | |
80 | /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ | |
81 | ||
82 | u32 shift = 32 - bits; | |
83 | /* clock starts at inactive polarity */ | |
84 | for (; likely(bits); bits--) { | |
85 | ||
86 | /* setup LSB (to slave) on leading edge */ | |
87 | if ((flags & SPI_MASTER_NO_TX) == 0) | |
88 | setmosi(data, (word & 1)); | |
89 | ||
90 | usleep_range(usecs, usecs + 1); /* T(setup) */ | |
91 | ||
92 | /* sample LSB (from slave) on trailing edge */ | |
93 | word >>= 1; | |
94 | if ((flags & SPI_MASTER_NO_RX) == 0) | |
95 | word |= (getmiso(data) << 31); | |
96 | ||
97 | setsck(data, !cpol); | |
98 | usleep_range(usecs, usecs + 1); | |
99 | ||
100 | setsck(data, cpol); | |
101 | } | |
102 | ||
103 | word >>= shift; | |
104 | return word; | |
105 | } | |
106 | ||
107 | static int | |
108 | spi_lp8841_rtc_transfer_one(struct spi_master *master, | |
109 | struct spi_device *spi, | |
110 | struct spi_transfer *t) | |
111 | { | |
112 | struct spi_lp8841_rtc *data = spi_master_get_devdata(master); | |
113 | unsigned count = t->len; | |
114 | const u8 *tx = t->tx_buf; | |
115 | u8 *rx = t->rx_buf; | |
116 | u8 word = 0; | |
117 | int ret = 0; | |
118 | ||
119 | if (tx) { | |
120 | data->state &= ~SPI_LP8841_RTC_nWE; | |
121 | writeb(data->state, data->iomem); | |
122 | while (likely(count > 0)) { | |
123 | word = *tx++; | |
124 | bitbang_txrx_be_cpha0_lsb(data, 1, 0, | |
125 | SPI_MASTER_NO_RX, word, 8); | |
126 | count--; | |
127 | } | |
128 | } else if (rx) { | |
129 | data->state |= SPI_LP8841_RTC_nWE; | |
130 | writeb(data->state, data->iomem); | |
131 | while (likely(count > 0)) { | |
132 | word = bitbang_txrx_be_cpha0_lsb(data, 1, 0, | |
133 | SPI_MASTER_NO_TX, word, 8); | |
134 | *rx++ = word; | |
135 | count--; | |
136 | } | |
137 | } else { | |
138 | ret = -EINVAL; | |
139 | } | |
140 | ||
141 | spi_finalize_current_transfer(master); | |
142 | ||
143 | return ret; | |
144 | } | |
145 | ||
146 | static void | |
147 | spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable) | |
148 | { | |
149 | struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master); | |
150 | ||
151 | data->state = 0; | |
152 | writeb(data->state, data->iomem); | |
153 | if (enable) { | |
154 | usleep_range(4, 5); | |
155 | data->state |= SPI_LP8841_RTC_CE; | |
156 | writeb(data->state, data->iomem); | |
157 | usleep_range(4, 5); | |
158 | } | |
159 | } | |
160 | ||
161 | static int | |
162 | spi_lp8841_rtc_setup(struct spi_device *spi) | |
163 | { | |
164 | if ((spi->mode & SPI_CS_HIGH) == 0) { | |
165 | dev_err(&spi->dev, "unsupported active low chip select\n"); | |
166 | return -EINVAL; | |
167 | } | |
168 | ||
169 | if ((spi->mode & SPI_LSB_FIRST) == 0) { | |
170 | dev_err(&spi->dev, "unsupported MSB first mode\n"); | |
171 | return -EINVAL; | |
172 | } | |
173 | ||
174 | if ((spi->mode & SPI_3WIRE) == 0) { | |
175 | dev_err(&spi->dev, "unsupported wiring. 3 wires required\n"); | |
176 | return -EINVAL; | |
177 | } | |
178 | ||
179 | return 0; | |
180 | } | |
181 | ||
182 | #ifdef CONFIG_OF | |
183 | static const struct of_device_id spi_lp8841_rtc_dt_ids[] = { | |
184 | { .compatible = "icpdas,lp8841-spi-rtc" }, | |
185 | { } | |
186 | }; | |
187 | ||
188 | MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids); | |
189 | #endif | |
190 | ||
191 | static int | |
192 | spi_lp8841_rtc_probe(struct platform_device *pdev) | |
193 | { | |
194 | int ret; | |
195 | struct spi_master *master; | |
196 | struct spi_lp8841_rtc *data; | |
197 | void *iomem; | |
198 | ||
199 | master = spi_alloc_master(&pdev->dev, sizeof(*data)); | |
200 | if (!master) | |
201 | return -ENOMEM; | |
202 | platform_set_drvdata(pdev, master); | |
203 | ||
204 | master->flags = SPI_MASTER_HALF_DUPLEX; | |
205 | master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST; | |
206 | ||
207 | master->bus_num = pdev->id; | |
208 | master->num_chipselect = 1; | |
209 | master->setup = spi_lp8841_rtc_setup; | |
210 | master->set_cs = spi_lp8841_rtc_set_cs; | |
211 | master->transfer_one = spi_lp8841_rtc_transfer_one; | |
212 | master->bits_per_word_mask = SPI_BPW_MASK(8); | |
213 | #ifdef CONFIG_OF | |
214 | master->dev.of_node = pdev->dev.of_node; | |
215 | #endif | |
216 | ||
217 | data = spi_master_get_devdata(master); | |
218 | ||
219 | iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0); | |
14a20428 AB |
220 | data->iomem = devm_ioremap_resource(&pdev->dev, iomem); |
221 | ret = PTR_ERR_OR_ZERO(data->iomem); | |
222 | if (ret) { | |
7ecbfff6 SI |
223 | dev_err(&pdev->dev, "failed to get IO address\n"); |
224 | goto err_put_master; | |
225 | } | |
226 | ||
227 | /* register with the SPI framework */ | |
228 | ret = devm_spi_register_master(&pdev->dev, master); | |
229 | if (ret) { | |
230 | dev_err(&pdev->dev, "cannot register spi master\n"); | |
231 | goto err_put_master; | |
232 | } | |
233 | ||
234 | return ret; | |
235 | ||
236 | ||
237 | err_put_master: | |
238 | spi_master_put(master); | |
239 | ||
240 | return ret; | |
241 | } | |
242 | ||
243 | MODULE_ALIAS("platform:" DRIVER_NAME); | |
244 | ||
245 | static struct platform_driver spi_lp8841_rtc_driver = { | |
246 | .driver = { | |
247 | .name = DRIVER_NAME, | |
248 | .of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids), | |
249 | }, | |
250 | .probe = spi_lp8841_rtc_probe, | |
251 | }; | |
252 | module_platform_driver(spi_lp8841_rtc_driver); | |
253 | ||
254 | MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC"); | |
255 | MODULE_AUTHOR("Sergei Ianovich"); | |
256 | MODULE_LICENSE("GPL"); |