GNU Linux-libre 4.19.286-gnu1
[releases.git] / arch / mips / lasat / ds1603.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Dallas Semiconductors 1603 RTC driver
4  *
5  * Brian Murphy <brian@murphy.dk>
6  *
7  */
8 #include <linux/kernel.h>
9 #include <asm/lasat/lasat.h>
10 #include <linux/delay.h>
11 #include <asm/lasat/ds1603.h>
12 #include <asm/time.h>
13
14 #include "ds1603.h"
15
16 #define READ_TIME_CMD 0x81
17 #define SET_TIME_CMD 0x80
18 #define TRIMMER_SET_CMD 0xC0
19 #define TRIMMER_VALUE_MASK 0x38
20 #define TRIMMER_SHIFT 3
21
22 struct ds_defs *ds1603;
23
24 /* HW specific register functions */
25 static void rtc_reg_write(unsigned long val)
26 {
27         *ds1603->reg = val;
28 }
29
30 static unsigned long rtc_reg_read(void)
31 {
32         unsigned long tmp = *ds1603->reg;
33         return tmp;
34 }
35
36 static unsigned long rtc_datareg_read(void)
37 {
38         unsigned long tmp = *ds1603->data_reg;
39         return tmp;
40 }
41
42 static void rtc_nrst_high(void)
43 {
44         rtc_reg_write(rtc_reg_read() | ds1603->rst);
45 }
46
47 static void rtc_nrst_low(void)
48 {
49         rtc_reg_write(rtc_reg_read() & ~ds1603->rst);
50 }
51
52 static void rtc_cycle_clock(unsigned long data)
53 {
54         data |= ds1603->clk;
55         rtc_reg_write(data);
56         lasat_ndelay(250);
57         if (ds1603->data_reversed)
58                 data &= ~ds1603->data;
59         else
60                 data |= ds1603->data;
61         data &= ~ds1603->clk;
62         rtc_reg_write(data);
63         lasat_ndelay(250 + ds1603->huge_delay);
64 }
65
66 static void rtc_write_databit(unsigned int bit)
67 {
68         unsigned long data = rtc_reg_read();
69         if (ds1603->data_reversed)
70                 bit = !bit;
71         if (bit)
72                 data |= ds1603->data;
73         else
74                 data &= ~ds1603->data;
75
76         rtc_reg_write(data);
77         lasat_ndelay(50 + ds1603->huge_delay);
78         rtc_cycle_clock(data);
79 }
80
81 static unsigned int rtc_read_databit(void)
82 {
83         unsigned int data;
84
85         data = (rtc_datareg_read() & (1 << ds1603->data_read_shift))
86                 >> ds1603->data_read_shift;
87         rtc_cycle_clock(rtc_reg_read());
88         return data;
89 }
90
91 static void rtc_write_byte(unsigned int byte)
92 {
93         int i;
94
95         for (i = 0; i <= 7; i++) {
96                 rtc_write_databit(byte & 1L);
97                 byte >>= 1;
98         }
99 }
100
101 static void rtc_write_word(unsigned long word)
102 {
103         int i;
104
105         for (i = 0; i <= 31; i++) {
106                 rtc_write_databit(word & 1L);
107                 word >>= 1;
108         }
109 }
110
111 static unsigned long rtc_read_word(void)
112 {
113         int i;
114         unsigned long word = 0;
115         unsigned long shift = 0;
116
117         for (i = 0; i <= 31; i++) {
118                 word |= rtc_read_databit() << shift;
119                 shift++;
120         }
121         return word;
122 }
123
124 static void rtc_init_op(void)
125 {
126         rtc_nrst_high();
127
128         rtc_reg_write(rtc_reg_read() & ~ds1603->clk);
129
130         lasat_ndelay(50);
131 }
132
133 static void rtc_end_op(void)
134 {
135         rtc_nrst_low();
136         lasat_ndelay(1000);
137 }
138
139 void read_persistent_clock64(struct timespec64 *ts)
140 {
141         unsigned long word;
142         unsigned long flags;
143
144         spin_lock_irqsave(&rtc_lock, flags);
145         rtc_init_op();
146         rtc_write_byte(READ_TIME_CMD);
147         word = rtc_read_word();
148         rtc_end_op();
149         spin_unlock_irqrestore(&rtc_lock, flags);
150
151         ts->tv_sec = word;
152         ts->tv_nsec = 0;
153 }
154
155 int update_persistent_clock64(struct timespec64 now)
156 {
157         time64_t time = now.tv_sec;
158         unsigned long flags;
159
160         spin_lock_irqsave(&rtc_lock, flags);
161         rtc_init_op();
162         rtc_write_byte(SET_TIME_CMD);
163         /*
164          * Due to the hardware limitation, we cast to 'unsigned long' type,
165          * so it will overflow in year 2106 on 32-bit machine.
166          */
167         rtc_write_word((unsigned long)time);
168         rtc_end_op();
169         spin_unlock_irqrestore(&rtc_lock, flags);
170
171         return 0;
172 }
173
174 void ds1603_set_trimmer(unsigned int trimval)
175 {
176         rtc_init_op();
177         rtc_write_byte(((trimval << TRIMMER_SHIFT) & TRIMMER_VALUE_MASK)
178                         | (TRIMMER_SET_CMD));
179         rtc_end_op();
180 }
181
182 void ds1603_disable(void)
183 {
184         ds1603_set_trimmer(TRIMMER_DISABLE_RTC);
185 }
186
187 void ds1603_enable(void)
188 {
189         ds1603_set_trimmer(TRIMMER_DEFAULT);
190 }