/drivers/i2c/busses/i2c-acorn.c

 1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 *  ARM IOC/IOMD i2c driver.
 4 *
 5 *  Copyright (C) 2000 Russell King
 6 *
 7 *  On Acorn machines, the following i2c devices are on the bus:
 8 *	- PCF8583 real time clock & static RAM
 9 */
10#include <linux/module.h>
11#include <linux/i2c.h>
12#include <linux/i2c-algo-bit.h>
13#include <linux/io.h>
14
15#include <mach/hardware.h>
16#include <asm/hardware/ioc.h>
17
18#define FORCE_ONES	0xdc
19#define SCL		0x02
20#define SDA		0x01
21
22/*
23 * We must preserve all non-i2c output bits in IOC_CONTROL.
24 * Note also that we need to preserve the value of SCL and
25 * SDA outputs as well (which may be different from the
26 * values read back from IOC_CONTROL).
27 */
28static u_int force_ones;
29
30static void ioc_setscl(void *data, int state)
31{
32	u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
33	u_int ones = force_ones;
34
35	if (state)
36		ones |= SCL;
37	else
38		ones &= ~SCL;
39
40	force_ones = ones;
41
42 	ioc_writeb(ioc_control | ones, IOC_CONTROL);
43}
44
45static void ioc_setsda(void *data, int state)
46{
47	u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
48	u_int ones = force_ones;
49
50	if (state)
51		ones |= SDA;
52	else
53		ones &= ~SDA;
54
55	force_ones = ones;
56
57 	ioc_writeb(ioc_control | ones, IOC_CONTROL);
58}
59
60static int ioc_getscl(void *data)
61{
62	return (ioc_readb(IOC_CONTROL) & SCL) != 0;
63}
64
65static int ioc_getsda(void *data)
66{
67	return (ioc_readb(IOC_CONTROL) & SDA) != 0;
68}
69
70static struct i2c_algo_bit_data ioc_data = {
71	.setsda		= ioc_setsda,
72	.setscl		= ioc_setscl,
73	.getsda		= ioc_getsda,
74	.getscl		= ioc_getscl,
75	.udelay		= 80,
76	.timeout	= HZ,
77};
78
79static struct i2c_adapter ioc_ops = {
80	.nr			= 0,
81	.name			= "ioc",
82	.algo_data		= &ioc_data,
83};
84
85static int __init i2c_ioc_init(void)
86{
87	force_ones = FORCE_ONES | SCL | SDA;
88
89	return i2c_bit_add_numbered_bus(&ioc_ops);
90}
91
92module_init(i2c_ioc_init);
93
94MODULE_AUTHOR("Russell King <linux@armlinux.org.uk>");
95MODULE_DESCRIPTION("ARM IOC/IOMD i2c driver");
96MODULE_LICENSE("GPL v2");