arch/mips/lasat/at93c.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Atmel AT93C46 serial eeprom driver
   4  *
   5  * Brian Murphy <brian.murphy@eicon.com>
   6  *
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/delay.h>
  10 #include <asm/lasat/lasat.h>
  11
  12 #include "at93c.h"
  13
  14 #define AT93C_ADDR_SHIFT        7
  15 #define AT93C_ADDR_MAX          ((1 << AT93C_ADDR_SHIFT) - 1)
  16 #define AT93C_RCMD              (0x6 << AT93C_ADDR_SHIFT)
  17 #define AT93C_WCMD              (0x5 << AT93C_ADDR_SHIFT)
  18 #define AT93C_WENCMD            0x260
  19 #define AT93C_WDSCMD            0x200
  20
  21 struct at93c_defs *at93c;
  22
  23 static void at93c_reg_write(u32 val)
  24 {
  25         *at93c->reg = val;
  26 }
  27
  28 static u32 at93c_reg_read(void)
  29 {
  30         u32 tmp = *at93c->reg;
  31         return tmp;
  32 }
  33
  34 static u32 at93c_datareg_read(void)
  35 {
  36         u32 tmp = *at93c->rdata_reg;
  37         return tmp;
  38 }
  39
  40 static void at93c_cycle_clk(u32 data)
  41 {
  42         at93c_reg_write(data | at93c->clk);
  43         lasat_ndelay(250);
  44         at93c_reg_write(data & ~at93c->clk);
  45         lasat_ndelay(250);
  46 }
  47
  48 static void at93c_write_databit(u8 bit)
  49 {
  50         u32 data = at93c_reg_read();
  51         if (bit)
  52                 data |= 1 << at93c->wdata_shift;
  53         else
  54                 data &= ~(1 << at93c->wdata_shift);
  55
  56         at93c_reg_write(data);
  57         lasat_ndelay(100);
  58         at93c_cycle_clk(data);
  59 }
  60
  61 static unsigned int at93c_read_databit(void)
  62 {
  63         u32 data;
  64
  65         at93c_cycle_clk(at93c_reg_read());
  66         data = (at93c_datareg_read() >> at93c->rdata_shift) & 1;
  67         return data;
  68 }
  69
  70 static u8 at93c_read_byte(void)
  71 {
  72         int i;
  73         u8 data = 0;
  74
  75         for (i = 0; i <= 7; i++) {
  76                 data <<= 1;
  77                 data |= at93c_read_databit();
  78         }
  79         return data;
  80 }
  81
  82 static void at93c_write_bits(u32 data, int size)
  83 {
  84         int i;
  85         int shift = size - 1;
  86         u32 mask = (1 << shift);
  87
  88         for (i = 0; i < size; i++) {
  89                 at93c_write_databit((data & mask) >> shift);
  90                 data <<= 1;
  91         }
  92 }
  93
  94 static void at93c_init_op(void)
  95 {
  96         at93c_reg_write((at93c_reg_read() | at93c->cs) &
  97                         ~at93c->clk & ~(1 << at93c->rdata_shift));
  98         lasat_ndelay(50);
  99 }
 100
 101 static void at93c_end_op(void)
 102 {
 103         at93c_reg_write(at93c_reg_read() & ~at93c->cs);
 104         lasat_ndelay(250);
 105 }
 106
 107 static void at93c_wait(void)
 108 {
 109         at93c_init_op();
 110         while (!at93c_read_databit())
 111                 ;
 112         at93c_end_op();
 113 };
 114
 115 static void at93c_disable_wp(void)
 116 {
 117         at93c_init_op();
 118         at93c_write_bits(AT93C_WENCMD, 10);
 119         at93c_end_op();
 120 }
 121
 122 static void at93c_enable_wp(void)
 123 {
 124         at93c_init_op();
 125         at93c_write_bits(AT93C_WDSCMD, 10);
 126         at93c_end_op();
 127 }
 128
 129 u8 at93c_read(u8 addr)
 130 {
 131         u8 byte;
 132         at93c_init_op();
 133         at93c_write_bits((addr & AT93C_ADDR_MAX)|AT93C_RCMD, 10);
 134         byte = at93c_read_byte();
 135         at93c_end_op();
 136         return byte;
 137 }
 138
 139 void at93c_write(u8 addr, u8 data)
 140 {
 141         at93c_disable_wp();
 142         at93c_init_op();
 143         at93c_write_bits((addr & AT93C_ADDR_MAX)|AT93C_WCMD, 10);
 144         at93c_write_bits(data, 8);
 145         at93c_end_op();
 146         at93c_wait();
 147         at93c_enable_wp();
 148 }