i2c/busses/i2c-at91-slave.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  *  i2c slave support for Atmel's AT91 Two-Wire Interface (TWI)
0004  *
0005  *  Copyright (C) 2017 Juergen Fitschen <me@jue.yt>
0006  */
0007
0008 #include <linux/err.h>
0009 #include <linux/i2c.h>
0010 #include <linux/interrupt.h>
0011 #include <linux/pm_runtime.h>
0012
0013 #include "i2c-at91.h"
0014
0015 static irqreturn_t atmel_twi_interrupt_slave(int irq, void *dev_id)
0016 {
0017     struct at91_twi_dev *dev = dev_id;
0018     const unsigned status = at91_twi_read(dev, AT91_TWI_SR);
0019     const unsigned irqstatus = status & at91_twi_read(dev, AT91_TWI_IMR);
0020     u8 value;
0021
0022     if (!irqstatus)
0023         return IRQ_NONE;
0024
0025     /* slave address has been detected on I2C bus */
0026     if (irqstatus & AT91_TWI_SVACC) {
0027         if (status & AT91_TWI_SVREAD) {
0028             i2c_slave_event(dev->slave,
0029                     I2C_SLAVE_READ_REQUESTED, &value);
0030             writeb_relaxed(value, dev->base + AT91_TWI_THR);
0031             at91_twi_write(dev, AT91_TWI_IER,
0032                        AT91_TWI_TXRDY | AT91_TWI_EOSACC);
0033         } else {
0034             i2c_slave_event(dev->slave,
0035                     I2C_SLAVE_WRITE_REQUESTED, &value);
0036             at91_twi_write(dev, AT91_TWI_IER,
0037                        AT91_TWI_RXRDY | AT91_TWI_EOSACC);
0038         }
0039         at91_twi_write(dev, AT91_TWI_IDR, AT91_TWI_SVACC);
0040     }
0041
0042     /* byte transmitted to remote master */
0043     if (irqstatus & AT91_TWI_TXRDY) {
0044         i2c_slave_event(dev->slave, I2C_SLAVE_READ_PROCESSED, &value);
0045         writeb_relaxed(value, dev->base + AT91_TWI_THR);
0046     }
0047
0048     /* byte received from remote master */
0049     if (irqstatus & AT91_TWI_RXRDY) {
0050         value = readb_relaxed(dev->base + AT91_TWI_RHR);
0051         i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
0052     }
0053
0054     /* master sent stop */
0055     if (irqstatus & AT91_TWI_EOSACC) {
0056         at91_twi_write(dev, AT91_TWI_IDR,
0057                    AT91_TWI_TXRDY | AT91_TWI_RXRDY | AT91_TWI_EOSACC);
0058         at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
0059         i2c_slave_event(dev->slave, I2C_SLAVE_STOP, &value);
0060     }
0061
0062     return IRQ_HANDLED;
0063 }
0064
0065 static int at91_reg_slave(struct i2c_client *slave)
0066 {
0067     struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
0068
0069     if (dev->slave)
0070         return -EBUSY;
0071
0072     if (slave->flags & I2C_CLIENT_TEN)
0073         return -EAFNOSUPPORT;
0074
0075     /* Make sure twi_clk doesn't get turned off! */
0076     pm_runtime_get_sync(dev->dev);
0077
0078     dev->slave = slave;
0079     dev->smr = AT91_TWI_SMR_SADR(slave->addr);
0080
0081     at91_init_twi_bus(dev);
0082     at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_SVACC);
0083
0084     dev_info(dev->dev, "entered slave mode (ADR=%d)\n", slave->addr);
0085
0086     return 0;
0087 }
0088
0089 static int at91_unreg_slave(struct i2c_client *slave)
0090 {
0091     struct at91_twi_dev *dev = i2c_get_adapdata(slave->adapter);
0092
0093     WARN_ON(!dev->slave);
0094
0095     dev_info(dev->dev, "leaving slave mode\n");
0096
0097     dev->slave = NULL;
0098     dev->smr = 0;
0099
0100     at91_init_twi_bus(dev);
0101
0102     pm_runtime_put(dev->dev);
0103
0104     return 0;
0105 }
0106
0107 static u32 at91_twi_func(struct i2c_adapter *adapter)
0108 {
0109     return I2C_FUNC_SLAVE | I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
0110         | I2C_FUNC_SMBUS_READ_BLOCK_DATA;
0111 }
0112
0113 static const struct i2c_algorithm at91_twi_algorithm_slave = {
0114     .reg_slave  = at91_reg_slave,
0115     .unreg_slave    = at91_unreg_slave,
0116     .functionality  = at91_twi_func,
0117 };
0118
0119 int at91_twi_probe_slave(struct platform_device *pdev,
0120              u32 phy_addr, struct at91_twi_dev *dev)
0121 {
0122     int rc;
0123
0124     rc = devm_request_irq(&pdev->dev, dev->irq, atmel_twi_interrupt_slave,
0125                   0, dev_name(dev->dev), dev);
0126     if (rc) {
0127         dev_err(dev->dev, "Cannot get irq %d: %d\n", dev->irq, rc);
0128         return rc;
0129     }
0130
0131     dev->adapter.algo = &at91_twi_algorithm_slave;
0132
0133     return 0;
0134 }
0135
0136 void at91_init_twi_bus_slave(struct at91_twi_dev *dev)
0137 {
0138     at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSDIS);
0139     if (dev->slave_detected && dev->smr) {
0140         at91_twi_write(dev, AT91_TWI_SMR, dev->smr);
0141         at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVEN);
0142     }
0143 }