1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * i2c slave support for Atmel's AT91 Two-Wire Interface (TWI)
4 *
5 * Copyright (C) 2017 Juergen Fitschen <me@jue.yt>
6 */
7
8 #include <linux/err.h>
9 #include <linux/i2c.h>
10 #include <linux/interrupt.h>
11 #include <linux/pm_runtime.h>
12
13 #include "i2c-at91.h"
14
atmel_twi_interrupt_slave(int irq,void * dev_id)15 static irqreturn_t atmel_twi_interrupt_slave(int irq, void *dev_id)
16 {
17 struct at91_twi_dev *dev = dev_id;
18 const unsigned status = at91_twi_read(dev, AT91_TWI_SR);
19 const unsigned irqstatus = status & at91_twi_read(dev, AT91_TWI_IMR);
20 u8 value;
21
22 if (!irqstatus)
23 return IRQ_NONE;
24
25 /* slave address has been detected on I2C bus */
26 if (irqstatus & AT91_TWI_SVACC) {
27 if (status & AT91_TWI_SVREAD) {
28 i2c_slave_event(dev->slave,
29 I2C_SLAVE_READ_REQUESTED, &value);
30 writeb_relaxed(value, dev->base + AT91_TWI_THR);
31 at91_twi_write(dev, AT91_TWI_IER,
32 AT91_TWI_TXRDY | AT91_TWI_EOSACC);
33 } else {
34 i2c_slave_event(dev->slave,
35 I2C_SLAVE_WRITE_REQUESTED, &value);
36 at91_twi_write(dev, AT91_TWI_IER,
37 AT91_TWI_RXRDY | AT91_TWI_EOSACC);
38 }
39 at91_twi_write(dev, AT91_TWI_IDR, AT91_TWI_SVACC);
40 }
41
42 /* byte transmitted to remote master */
43 if (irqstatus & AT91_TWI_TXRDY) {
44 i2c_slave_event(dev->slave, I2C_SLAVE_READ_PROCESSED, &value);
45 writeb_relaxed(value, dev->base + AT91_TWI_THR);
46 }
47
48 /* byte received from remote master */
49 if (irqstatus & AT91_TWI_RXRDY) {
50 value = readb_relaxed(dev->base + AT91_TWI_RHR);
51 i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
52 }
53
54 /* master sent stop */
55 if (irqstatus & AT91_TWI_EOSACC) {
56 at91_twi_write(dev, AT91_TWI_IDR,
57 AT91_TWI_TXRDY | AT91_TWI_RXRDY | AT91_TWI_EOSACC);
58 at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
59 i2c_slave_event(dev->slave, I2C_SLAVE_STOP, &value);
60 }
61
62 return IRQ_HANDLED;
63 }
64
at91_reg_slave(struct i2c_client * slave)65 static int at91_reg_slave(struct i2c_client *slave)
66 {
67 struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
68
69 if (dev->slave)
70 return -EBUSY;
71
72 if (slave->flags & I2C_CLIENT_TEN)
73 return -EAFNOSUPPORT;
74
75 /* Make sure twi_clk doesn't get turned off! */
76 pm_runtime_get_sync(dev->dev);
77
78 dev->slave = slave;
79 dev->smr = AT91_TWI_SMR_SADR(slave->addr);
80
81 at91_init_twi_bus(dev);
82 at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
83
84 dev_info(dev->dev, "entered slave mode (ADR=%d)\n", slave->addr);
85
86 return 0;
87 }
88
at91_unreg_slave(struct i2c_client * slave)89 static int at91_unreg_slave(struct i2c_client *slave)
90 {
91 struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
92
93 WARN_ON(!dev->slave);
94
95 dev_info(dev->dev, "leaving slave mode\n");
96
97 dev->slave = NULL;
98 dev->smr = 0;
99
100 at91_init_twi_bus(dev);
101
102 pm_runtime_put(dev->dev);
103
104 return 0;
105 }
106
at91_twi_func(struct i2c_adapter * adapter)107 static u32 at91_twi_func(struct i2c_adapter *adapter)
108 {
109 return I2C_FUNC_SLAVE | I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
110 | I2C_FUNC_SMBUS_READ_BLOCK_DATA;
111 }
112
113 static const struct i2c_algorithm at91_twi_algorithm_slave = {
114 .reg_slave = at91_reg_slave,
115 .unreg_slave = at91_unreg_slave,
116 .functionality = at91_twi_func,
117 };
118
at91_twi_probe_slave(struct platform_device * pdev,u32 phy_addr,struct at91_twi_dev * dev)119 int at91_twi_probe_slave(struct platform_device *pdev,
120 u32 phy_addr, struct at91_twi_dev *dev)
121 {
122 int rc;
123
124 rc = devm_request_irq(&pdev->dev, dev->irq, atmel_twi_interrupt_slave,
125 0, dev_name(dev->dev), dev);
126 if (rc) {
127 dev_err(dev->dev, "Cannot get irq %d: %d\n", dev->irq, rc);
128 return rc;
129 }
130
131 dev->adapter.algo = &at91_twi_algorithm_slave;
132
133 return 0;
134 }
135
at91_init_twi_bus_slave(struct at91_twi_dev * dev)136 void at91_init_twi_bus_slave(struct at91_twi_dev *dev)
137 {
138 at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSDIS);
139 if (dev->slave_detected && dev->smr) {
140 at91_twi_write(dev, AT91_TWI_SMR, dev->smr);
141 at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVEN);
142 }
143 }
144
