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17#include <linux/module.h>
18#include <linux/kernel.h>
19#include <linux/device.h>
20#include <linux/printk.h>
21#include <linux/spi/spi.h>
22#include <linux/rtc.h>
23#include <linux/of.h>
24
25
26#define MCP795_EEREAD 0x03
27#define MCP795_EEWRITE 0x02
28#define MCP795_EEWRDI 0x04
29#define MCP795_EEWREN 0x06
30#define MCP795_SRREAD 0x05
31#define MCP795_SRWRITE 0x01
32#define MCP795_READ 0x13
33#define MCP795_WRITE 0x12
34#define MCP795_UNLOCK 0x14
35#define MCP795_IDWRITE 0x32
36#define MCP795_IDREAD 0x33
37#define MCP795_CLRWDT 0x44
38#define MCP795_CLRRAM 0x54
39
40#define MCP795_ST_BIT 0x80
41#define MCP795_24_BIT 0x40
42
43static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count)
44{
45 struct spi_device *spi = to_spi_device(dev);
46 int ret;
47 u8 tx[2];
48
49 tx[0] = MCP795_READ;
50 tx[1] = addr;
51 ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count);
52
53 if (ret)
54 dev_err(dev, "Failed reading %d bytes from address %x.\n",
55 count, addr);
56
57 return ret;
58}
59
60static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count)
61{
62 struct spi_device *spi = to_spi_device(dev);
63 int ret;
64 u8 tx[2 + count];
65
66 tx[0] = MCP795_WRITE;
67 tx[1] = addr;
68 memcpy(&tx[2], data, count);
69
70 ret = spi_write(spi, tx, 2 + count);
71
72 if (ret)
73 dev_err(dev, "Failed to write %d bytes to address %x.\n",
74 count, addr);
75
76 return ret;
77}
78
79static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state)
80{
81 int ret;
82 u8 tmp;
83
84 ret = mcp795_rtcc_read(dev, addr, &tmp, 1);
85 if (ret)
86 return ret;
87
88 if ((tmp & mask) != state) {
89 tmp = (tmp & ~mask) | state;
90 ret = mcp795_rtcc_write(dev, addr, &tmp, 1);
91 }
92
93 return ret;
94}
95
96static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
97{
98 int ret;
99 u8 data[7];
100
101
102 ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data));
103
104 if (ret)
105 return ret;
106
107 data[0] = (data[0] & 0x80) | ((tim->tm_sec / 10) << 4) | (tim->tm_sec % 10);
108 data[1] = (data[1] & 0x80) | ((tim->tm_min / 10) << 4) | (tim->tm_min % 10);
109 data[2] = ((tim->tm_hour / 10) << 4) | (tim->tm_hour % 10);
110 data[4] = ((tim->tm_mday / 10) << 4) | ((tim->tm_mday) % 10);
111 data[5] = (data[5] & 0x10) | (tim->tm_mon / 10) | (tim->tm_mon % 10);
112
113 if (tim->tm_year > 100)
114 tim->tm_year -= 100;
115
116 data[6] = ((tim->tm_year / 10) << 4) | (tim->tm_year % 10);
117
118 ret = mcp795_rtcc_write(dev, 0x01, data, sizeof(data));
119
120 if (ret)
121 return ret;
122
123 dev_dbg(dev, "Set mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
124 tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
125 tim->tm_hour, tim->tm_min, tim->tm_sec);
126
127 return 0;
128}
129
130static int mcp795_read_time(struct device *dev, struct rtc_time *tim)
131{
132 int ret;
133 u8 data[7];
134
135 ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data));
136
137 if (ret)
138 return ret;
139
140 tim->tm_sec = ((data[0] & 0x70) >> 4) * 10 + (data[0] & 0x0f);
141 tim->tm_min = ((data[1] & 0x70) >> 4) * 10 + (data[1] & 0x0f);
142 tim->tm_hour = ((data[2] & 0x30) >> 4) * 10 + (data[2] & 0x0f);
143 tim->tm_mday = ((data[4] & 0x30) >> 4) * 10 + (data[4] & 0x0f);
144 tim->tm_mon = ((data[5] & 0x10) >> 4) * 10 + (data[5] & 0x0f);
145 tim->tm_year = ((data[6] & 0xf0) >> 4) * 10 + (data[6] & 0x0f) + 100;
146
147 dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
148 tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
149 tim->tm_hour, tim->tm_min, tim->tm_sec);
150
151 return rtc_valid_tm(tim);
152}
153
154static const struct rtc_class_ops mcp795_rtc_ops = {
155 .read_time = mcp795_read_time,
156 .set_time = mcp795_set_time
157};
158
159static int mcp795_probe(struct spi_device *spi)
160{
161 struct rtc_device *rtc;
162 int ret;
163
164 spi->mode = SPI_MODE_0;
165 spi->bits_per_word = 8;
166 ret = spi_setup(spi);
167 if (ret) {
168 dev_err(&spi->dev, "Unable to setup SPI\n");
169 return ret;
170 }
171
172
173 mcp795_rtcc_set_bits(&spi->dev, 0x01, MCP795_ST_BIT, MCP795_ST_BIT);
174
175 mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0);
176
177 rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795",
178 &mcp795_rtc_ops, THIS_MODULE);
179 if (IS_ERR(rtc))
180 return PTR_ERR(rtc);
181
182 spi_set_drvdata(spi, rtc);
183
184 return 0;
185}
186
187#ifdef CONFIG_OF
188static const struct of_device_id mcp795_of_match[] = {
189 { .compatible = "maxim,mcp795" },
190 { }
191};
192MODULE_DEVICE_TABLE(of, mcp795_of_match);
193#endif
194
195static struct spi_driver mcp795_driver = {
196 .driver = {
197 .name = "rtc-mcp795",
198 .of_match_table = of_match_ptr(mcp795_of_match),
199 },
200 .probe = mcp795_probe,
201};
202
203module_spi_driver(mcp795_driver);
204
205MODULE_DESCRIPTION("MCP795 RTC SPI Driver");
206MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>");
207MODULE_LICENSE("GPL");
208MODULE_ALIAS("spi:mcp795");
209
