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
 15static 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
 65static 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
 89static 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
107static 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
113static 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
119int 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
136void 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}