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;
110 }
111 
112 static const struct i2c_algorithm at91_twi_algorithm_slave = {
113 	.reg_slave	= at91_reg_slave,
114 	.unreg_slave	= at91_unreg_slave,
115 	.functionality	= at91_twi_func,
116 };
117 
at91_twi_probe_slave(struct platform_device * pdev,u32 phy_addr,struct at91_twi_dev * dev)118 int at91_twi_probe_slave(struct platform_device *pdev,
119 			 u32 phy_addr, struct at91_twi_dev *dev)
120 {
121 	int rc;
122 
123 	rc = devm_request_irq(&pdev->dev, dev->irq, atmel_twi_interrupt_slave,
124 			      0, dev_name(dev->dev), dev);
125 	if (rc) {
126 		dev_err(dev->dev, "Cannot get irq %d: %d\n", dev->irq, rc);
127 		return rc;
128 	}
129 
130 	dev->adapter.algo = &at91_twi_algorithm_slave;
131 
132 	return 0;
133 }
134 
at91_init_twi_bus_slave(struct at91_twi_dev * dev)135 void at91_init_twi_bus_slave(struct at91_twi_dev *dev)
136 {
137 	at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSDIS);
138 	if (dev->slave_detected && dev->smr) {
139 		at91_twi_write(dev, AT91_TWI_SMR, dev->smr);
140 		at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVEN);
141 	}
142 }
143