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// SPDX-License-Identifier: GPL-2.0
/*
* i2c slave support for Atmel's AT91 Two-Wire Interface (TWI)
*
* Copyright (C) 2017 Juergen Fitschen <me@jue.yt>
*/
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/pm_runtime.h>
#include "i2c-at91.h"
static irqreturn_t atmel_twi_interrupt_slave(int irq, void *dev_id)
{
struct at91_twi_dev *dev = dev_id;
const unsigned status = at91_twi_read(dev, AT91_TWI_SR);
const unsigned irqstatus = status & at91_twi_read(dev, AT91_TWI_IMR);
u8 value;
if (!irqstatus)
return IRQ_NONE;
/* slave address has been detected on I2C bus */
if (irqstatus & AT91_TWI_SVACC) {
if (status & AT91_TWI_SVREAD) {
i2c_slave_event(dev->slave,
I2C_SLAVE_READ_REQUESTED, &value);
writeb_relaxed(value, dev->base + AT91_TWI_THR);
at91_twi_write(dev, AT91_TWI_IER,
AT91_TWI_TXRDY | AT91_TWI_EOSACC);
} else {
i2c_slave_event(dev->slave,
I2C_SLAVE_WRITE_REQUESTED, &value);
at91_twi_write(dev, AT91_TWI_IER,
AT91_TWI_RXRDY | AT91_TWI_EOSACC);
}
at91_twi_write(dev, AT91_TWI_IDR, AT91_TWI_SVACC);
}
/* byte transmitted to remote master */
if (irqstatus & AT91_TWI_TXRDY) {
i2c_slave_event(dev->slave, I2C_SLAVE_READ_PROCESSED, &value);
writeb_relaxed(value, dev->base + AT91_TWI_THR);
}
/* byte received from remote master */
if (irqstatus & AT91_TWI_RXRDY) {
value = readb_relaxed(dev->base + AT91_TWI_RHR);
i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
}
/* master sent stop */
if (irqstatus & AT91_TWI_EOSACC) {
at91_twi_write(dev, AT91_TWI_IDR,
AT91_TWI_TXRDY | AT91_TWI_RXRDY | AT91_TWI_EOSACC);
at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
i2c_slave_event(dev->slave, I2C_SLAVE_STOP, &value);
}
return IRQ_HANDLED;
}
static int at91_reg_slave(struct i2c_client *slave)
{
struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
if (dev->slave)
return -EBUSY;
if (slave->flags & I2C_CLIENT_TEN)
return -EAFNOSUPPORT;
/* Make sure twi_clk doesn't get turned off! */
pm_runtime_get_sync(dev->dev);
dev->slave = slave;
dev->smr = AT91_TWI_SMR_SADR(slave->addr);
at91_init_twi_bus(dev);
at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
dev_info(dev->dev, "entered slave mode (ADR=%d)\n", slave->addr);
return 0;
}
static int at91_unreg_slave(struct i2c_client *slave)
{
struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
WARN_ON(!dev->slave);
dev_info(dev->dev, "leaving slave mode\n");
dev->slave = NULL;
dev->smr = 0;
at91_init_twi_bus(dev);
pm_runtime_put(dev->dev);
return 0;
}
static u32 at91_twi_func(struct i2c_adapter *adapter)
{
return I2C_FUNC_SLAVE;
}
static const struct i2c_algorithm at91_twi_algorithm_slave = {
.reg_slave = at91_reg_slave,
.unreg_slave = at91_unreg_slave,
.functionality = at91_twi_func,
};
int at91_twi_probe_slave(struct platform_device *pdev,
u32 phy_addr, struct at91_twi_dev *dev)
{
int rc;
rc = devm_request_irq(&pdev->dev, dev->irq, atmel_twi_interrupt_slave,
0, dev_name(dev->dev), dev);
if (rc) {
dev_err(dev->dev, "Cannot get irq %d: %d\n", dev->irq, rc);
return rc;
}
dev->adapter.algo = &at91_twi_algorithm_slave;
return 0;
}
void at91_init_twi_bus_slave(struct at91_twi_dev *dev)
{
at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSDIS);
if (dev->slave_detected && dev->smr) {
at91_twi_write(dev, AT91_TWI_SMR, dev->smr);
at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVEN);
}
}
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