arch/mips/lasat/ds1603.c

   1 /*
   2  * Dallas Semiconductors 1603 RTC driver
   3  *
   4  * Brian Murphy <brian@murphy.dk>
   5  *
   6  */
   7 #include <linux/kernel.h>
   8 #include <asm/lasat/lasat.h>
   9 #include <linux/delay.h>
  10 #include <asm/lasat/ds1603.h>
  11
  12 #include "ds1603.h"
  13
  14 #define READ_TIME_CMD 0x81
  15 #define SET_TIME_CMD 0x80
  16 #define TRIMMER_SET_CMD 0xC0
  17 #define TRIMMER_VALUE_MASK 0x38
  18 #define TRIMMER_SHIFT 3
  19
  20 struct ds_defs *ds1603 = NULL;
  21
  22 /* HW specific register functions */
  23 static void rtc_reg_write(unsigned long val)
  24 {
  25         *ds1603->reg = val;
  26 }
  27
  28 static unsigned long rtc_reg_read(void)
  29 {
  30         unsigned long tmp = *ds1603->reg;
  31         return tmp;
  32 }
  33
  34 static unsigned long rtc_datareg_read(void)
  35 {
  36         unsigned long tmp = *ds1603->data_reg;
  37         return tmp;
  38 }
  39
  40 static void rtc_nrst_high(void)
  41 {
  42         rtc_reg_write(rtc_reg_read() | ds1603->rst);
  43 }
  44
  45 static void rtc_nrst_low(void)
  46 {
  47         rtc_reg_write(rtc_reg_read() & ~ds1603->rst);
  48 }
  49
  50 static void rtc_cycle_clock(unsigned long data)
  51 {
  52         data |= ds1603->clk;
  53         rtc_reg_write(data);
  54         lasat_ndelay(250);
  55         if (ds1603->data_reversed)
  56                 data &= ~ds1603->data;
  57         else
  58                 data |= ds1603->data;
  59         data &= ~ds1603->clk;
  60         rtc_reg_write(data);
  61         lasat_ndelay(250 + ds1603->huge_delay);
  62 }
  63
  64 static void rtc_write_databit(unsigned int bit)
  65 {
  66         unsigned long data = rtc_reg_read();
  67         if (ds1603->data_reversed)
  68                 bit = !bit;
  69         if (bit)
  70                 data |= ds1603->data;
  71         else
  72                 data &= ~ds1603->data;
  73
  74         rtc_reg_write(data);
  75         lasat_ndelay(50 + ds1603->huge_delay);
  76         rtc_cycle_clock(data);
  77 }
  78
  79 static unsigned int rtc_read_databit(void)
  80 {
  81         unsigned int data;
  82
  83         data = (rtc_datareg_read() & (1 << ds1603->data_read_shift))
  84                 >> ds1603->data_read_shift;
  85         rtc_cycle_clock(rtc_reg_read());
  86         return data;
  87 }
  88
  89 static void rtc_write_byte(unsigned int byte)
  90 {
  91         int i;
  92
  93         for (i = 0; i<=7; i++) {
  94                 rtc_write_databit(byte & 1L);
  95                 byte >>= 1;
  96         }
  97 }
  98
  99 static void rtc_write_word(unsigned long word)
 100 {
 101         int i;
 102
 103         for (i = 0; i<=31; i++) {
 104                 rtc_write_databit(word & 1L);
 105                 word >>= 1;
 106         }
 107 }
 108
 109 static unsigned long rtc_read_word(void)
 110 {
 111         int i;
 112         unsigned long word = 0;
 113         unsigned long shift = 0;
 114
 115         for (i = 0; i<=31; i++) {
 116                 word |= rtc_read_databit() << shift;
 117                 shift++;
 118         }
 119         return word;
 120 }
 121
 122 static void rtc_init_op(void)
 123 {
 124         rtc_nrst_high();
 125
 126         rtc_reg_write(rtc_reg_read() & ~ds1603->clk);
 127
 128         lasat_ndelay(50);
 129 }
 130
 131 static void rtc_end_op(void)
 132 {
 133         rtc_nrst_low();
 134         lasat_ndelay(1000);
 135 }
 136
 137 /* interface */
 138 unsigned long ds1603_read(void)
 139 {
 140         unsigned long word;
 141         rtc_init_op();
 142         rtc_write_byte(READ_TIME_CMD);
 143         word = rtc_read_word();
 144         rtc_end_op();
 145         return word;
 146 }
 147
 148 int ds1603_set(unsigned long time)
 149 {
 150         rtc_init_op();
 151         rtc_write_byte(SET_TIME_CMD);
 152         rtc_write_word(time);
 153         rtc_end_op();
 154
 155         return 0;
 156 }
 157
 158 void ds1603_set_trimmer(unsigned int trimval)
 159 {
 160         rtc_init_op();
 161         rtc_write_byte(((trimval << TRIMMER_SHIFT) & TRIMMER_VALUE_MASK)
 162                         | (TRIMMER_SET_CMD));
 163         rtc_end_op();
 164 }
 165
 166 void ds1603_disable(void)
 167 {
 168         ds1603_set_trimmer(TRIMMER_DISABLE_RTC);
 169 }
 170
 171 void ds1603_enable(void)
 172 {
 173         ds1603_set_trimmer(TRIMMER_DEFAULT);
 174 }