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