1 // SPDX-License-Identifier: GPL-2.0-or-later
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
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
setsck(struct spi_lp8841_rtc * data,int is_on)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
setmosi(struct spi_lp8841_rtc * data,int is_on)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
getmiso(struct spi_lp8841_rtc * data)61 getmiso(struct spi_lp8841_rtc *data)
62 {
63 return ioread8(data->iomem) & SPI_LP8841_RTC_MISO;
64 }
65
66 static inline u32
bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc * data,unsigned usecs,unsigned cpol,unsigned flags,u32 word,u8 bits)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
spi_lp8841_rtc_transfer_one(struct spi_master * master,struct spi_device * spi,struct spi_transfer * t)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
spi_lp8841_rtc_set_cs(struct spi_device * spi,bool enable)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
spi_lp8841_rtc_setup(struct spi_device * spi)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
spi_lp8841_rtc_probe(struct platform_device * pdev)183 spi_lp8841_rtc_probe(struct platform_device *pdev)
184 {
185 int ret;
186 struct spi_master *master;
187 struct spi_lp8841_rtc *data;
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
209 data->iomem = devm_platform_ioremap_resource(pdev, 0);
210 ret = PTR_ERR_OR_ZERO(data->iomem);
211 if (ret) {
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");
246
