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 }