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
 21struct at93c_defs *at93c;
 22
 23static void at93c_reg_write(u32 val)
 24{
 25	*at93c->reg = val;
 26}
 27
 28static u32 at93c_reg_read(void)
 29{
 30	u32 tmp = *at93c->reg;
 31	return tmp;
 32}
 33
 34static u32 at93c_datareg_read(void)
 35{
 36	u32 tmp = *at93c->rdata_reg;
 37	return tmp;
 38}
 39
 40static 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
 48static 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
 61static 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
 70static 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
 82static 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
 94static 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
101static void at93c_end_op(void)
102{
103	at93c_reg_write(at93c_reg_read() & ~at93c->cs);
104	lasat_ndelay(250);
105}
106
107static void at93c_wait(void)
108{
109	at93c_init_op();
110	while (!at93c_read_databit())
111		;
112	at93c_end_op();
113};
114
115static void at93c_disable_wp(void)
116{
117	at93c_init_op();
118	at93c_write_bits(AT93C_WENCMD, 10);
119	at93c_end_op();
120}
121
122static void at93c_enable_wp(void)
123{
124	at93c_init_op();
125	at93c_write_bits(AT93C_WDSCMD, 10);
126	at93c_end_op();
127}
128
129u8 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
139void 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}