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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
40
41
42
43
44struct spi_lp8841_rtc {
45 void *iomem;
46 unsigned long state;
47};
48
49static inline void
50setsck(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
59static inline void
60setmosi(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
69static inline int
70getmiso(struct spi_lp8841_rtc *data)
71{
72 return ioread8(data->iomem) & SPI_LP8841_RTC_MISO;
73}
74
75static inline u32
76bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data,
77 unsigned usecs, unsigned cpol, unsigned flags,
78 u32 word, u8 bits)
79{
80
81
82 u32 shift = 32 - bits;
83
84 for (; likely(bits); bits--) {
85
86
87 if ((flags & SPI_MASTER_NO_TX) == 0)
88 setmosi(data, (word & 1));
89
90 usleep_range(usecs, usecs + 1);
91
92
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
107static int
108spi_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
146static void
147spi_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
161static int
162spi_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
183static const struct of_device_id spi_lp8841_rtc_dt_ids[] = {
184 { .compatible = "icpdas,lp8841-spi-rtc" },
185 { }
186};
187
188MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids);
189#endif
190
191static int
192spi_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);
220 data->iomem = devm_ioremap_resource(&pdev->dev, iomem);
221 ret = PTR_ERR_OR_ZERO(data->iomem);
222 if (ret) {
223 dev_err(&pdev->dev, "failed to get IO address\n");
224 goto err_put_master;
225 }
226
227
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
237err_put_master:
238 spi_master_put(master);
239
240 return ret;
241}
242
243MODULE_ALIAS("platform:" DRIVER_NAME);
244
245static 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};
252module_platform_driver(spi_lp8841_rtc_driver);
253
254MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC");
255MODULE_AUTHOR("Sergei Ianovich");
256MODULE_LICENSE("GPL");
257
