1 // SPDX-License-Identifier: GPL-2.0+
3 * Copyright (c) 2018 Arm Ltd.
4 * Author: Liviu Dudau <liviu.dudau@foss.arm.com>
14 #include <linux/bitops.h>
15 #include <linux/delay.h>
18 #define I2C_CONTROL_REG 0x00
19 #define I2C_SET_REG 0x00
20 #define I2C_CLEAR_REG 0x04
25 struct versatile_i2c_priv {
30 static inline void versatile_sda_set(struct versatile_i2c_priv *priv, u8 state)
32 writel(SDA, priv->base + (state ? I2C_SET_REG : I2C_CLEAR_REG));
36 static inline int versatile_sda_get(struct versatile_i2c_priv *priv)
38 int v = !!(readl(priv->base + I2C_CONTROL_REG) & SDA);
44 static inline void versatile_scl_set(struct versatile_i2c_priv *priv, u8 state)
46 writel(SCL, priv->base + (state ? I2C_SET_REG : I2C_CLEAR_REG));
50 static inline int versatile_scl_get(struct versatile_i2c_priv *priv)
52 int v = !!(readl(priv->base + I2C_CONTROL_REG) & SCL);
58 /* start: SDA goes from high to low while SCL is high */
59 static void versatile_i2c_start(struct versatile_i2c_priv *priv)
62 versatile_sda_set(priv, 1);
63 versatile_scl_set(priv, 1);
64 versatile_sda_set(priv, 0);
67 /* stop: SDA goes from low to high while SCL is high */
68 static void versatile_i2c_stop(struct versatile_i2c_priv *priv)
70 versatile_scl_set(priv, 0);
71 versatile_sda_set(priv, 0);
72 versatile_scl_set(priv, 1);
73 versatile_sda_set(priv, 1);
76 /* read a bit from the SDA line (data or ACK/NACK) */
77 static u8 versatile_i2c_read_bit(struct versatile_i2c_priv *priv)
79 versatile_scl_set(priv, 0);
80 versatile_sda_set(priv, 1);
81 versatile_scl_set(priv, 1);
83 return (u8)versatile_sda_get(priv);
86 /* write a bit on the SDA line */
87 static void versatile_i2c_write_bit(struct versatile_i2c_priv *priv, u8 bit)
89 versatile_scl_set(priv, 0);
90 versatile_sda_set(priv, bit);
91 versatile_scl_set(priv, 1);
95 /* send a reset sequence of 9 clocks with SDA high */
96 static void versatile_i2c_reset_bus(struct versatile_i2c_priv *priv)
100 for (i = 0; i < 9; i++)
101 versatile_i2c_write_bit(priv, 1);
103 versatile_i2c_stop(priv);
106 /* write byte without start/stop sequence */
107 static int versatile_i2c_write_byte(struct versatile_i2c_priv *priv, u8 byte)
111 for (i = 0; i < 8; i++) {
112 versatile_i2c_write_bit(priv, byte & 0x80);
117 nak = versatile_i2c_read_bit(priv);
118 versatile_scl_set(priv, 0);
120 return nak; /* not a nack is an ack */
123 static int versatile_i2c_read_byte(struct versatile_i2c_priv *priv,
129 for (i = 0; i < 8; i++) {
131 *byte |= versatile_i2c_read_bit(priv);
134 versatile_i2c_write_bit(priv, ack);
139 static int versatile_i2c_send_slave_addr(struct versatile_i2c_priv *priv,
145 if (msg->flags & I2C_M_TEN) {
146 /* 10-bit address, send extended address code first */
147 addr = 0xf0 | ((msg->addr >> 7) & 0x06);
148 ret = versatile_i2c_write_byte(priv, addr);
150 versatile_i2c_stop(priv);
155 ret = versatile_i2c_write_byte(priv, msg->addr & 0xff);
157 versatile_i2c_stop(priv);
160 /* reads need to resend the addr */
161 if (msg->flags & I2C_M_RD) {
162 versatile_i2c_start(priv);
164 ret = versatile_i2c_write_byte(priv, addr);
166 versatile_i2c_stop(priv);
171 /* normal 7-bit address */
172 addr = msg->addr << 1;
173 if (msg->flags & I2C_M_RD)
175 ret = versatile_i2c_write_byte(priv, addr);
177 versatile_i2c_stop(priv);
185 static int versatile_i2c_message_xfer(struct versatile_i2c_priv *priv,
191 versatile_i2c_start(priv);
192 if (versatile_i2c_send_slave_addr(priv, msg))
195 for (i = 0; i < msg->len; i++) {
196 if (msg->flags & I2C_M_RD) {
197 ack = (msg->len - i - 1) == 0 ? 1 : 0;
198 ret = versatile_i2c_read_byte(priv, &msg->buf[i], ack);
200 ret = versatile_i2c_write_byte(priv, msg->buf[i]);
207 versatile_i2c_stop(priv);
212 static int versatile_i2c_xfer(struct udevice *bus,
213 struct i2c_msg *msg, int nmsgs)
215 struct versatile_i2c_priv *priv = dev_get_priv(bus);
218 for ( ; nmsgs > 0; nmsgs--, msg++) {
219 ret = versatile_i2c_message_xfer(priv, msg);
227 static int versatile_i2c_chip_probe(struct udevice *bus,
228 uint chip, uint chip_flags)
230 /* probe the presence of a slave by writing a 0-size message */
231 struct i2c_msg msg = { .addr = chip, .flags = chip_flags,
232 .len = 0, .buf = NULL };
233 struct versatile_i2c_priv *priv = dev_get_priv(bus);
235 return versatile_i2c_message_xfer(priv, &msg);
238 static int versatile_i2c_set_bus_speed(struct udevice *bus, unsigned int speed)
240 struct versatile_i2c_priv *priv = dev_get_priv(bus);
242 priv->delay = 1000000 / (speed << 2);
244 versatile_i2c_reset_bus(priv);
249 static int versatile_i2c_probe(struct udevice *dev)
251 struct versatile_i2c_priv *priv = dev_get_priv(dev);
253 priv->base = (phys_addr_t)dev_read_addr(dev);
254 priv->delay = 25; /* 25us * 4 = 100kHz */
256 * U-Boot still doesn't assign automatically
257 * sequence numbers to devices
264 static const struct dm_i2c_ops versatile_i2c_ops = {
265 .xfer = versatile_i2c_xfer,
266 .probe_chip = versatile_i2c_chip_probe,
267 .set_bus_speed = versatile_i2c_set_bus_speed,
270 static const struct udevice_id versatile_i2c_of_match[] = {
271 { .compatible = "arm,versatile-i2c" },
275 U_BOOT_DRIVER(versatile_i2c) = {
276 .name = "i2c-bus-versatile",
278 .of_match = versatile_i2c_of_match,
279 .probe = versatile_i2c_probe,
280 .priv_auto_alloc_size = sizeof(struct versatile_i2c_priv),
281 .ops = &versatile_i2c_ops,