drivers/i2c/busses/i2c-at91-slave.c

   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
  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
  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
  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
 107 static 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
 113 static 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
 119 int 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
 136 void 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 }