Quelle  i2c-at91-slave.c   Sprache: C

// 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);
 }
}