i2c: npcm7xx: Add support for slave mode for Nuvoton
authorTali Perry <tali.perry1@gmail.com>
Wed, 27 May 2020 20:08:20 +0000 (23:08 +0300)
committerWolfram Sang <wsa@kernel.org>
Wed, 3 Jun 2020 20:39:16 +0000 (22:39 +0200)
Add support for slave mode for Nuvoton
NPCM BMC I2C controller driver.

Signed-off-by: Tali Perry <tali.perry1@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
drivers/i2c/busses/i2c-npcm7xx.c

index 018abf8..a8e75c3 100644 (file)
@@ -71,6 +71,24 @@ enum i2c_state {
        I2C_STOP_PENDING,
 };
 
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+/* Module supports setting multiple own slave addresses */
+enum i2c_addr {
+       I2C_SLAVE_ADDR1 = 0,
+       I2C_SLAVE_ADDR2,
+       I2C_SLAVE_ADDR3,
+       I2C_SLAVE_ADDR4,
+       I2C_SLAVE_ADDR5,
+       I2C_SLAVE_ADDR6,
+       I2C_SLAVE_ADDR7,
+       I2C_SLAVE_ADDR8,
+       I2C_SLAVE_ADDR9,
+       I2C_SLAVE_ADDR10,
+       I2C_GC_ADDR,
+       I2C_ARP_ADDR,
+};
+#endif
+
 /* init register and default value required to enable module */
 #define NPCM_I2CSEGCTL                 0xE4
 #define NPCM_I2CSEGCTL_INIT_VAL                0x0333F000
@@ -98,6 +116,21 @@ enum i2c_state {
 #define NPCM_I2CADDR6                  0x16
 #define NPCM_I2CADDR10                 0x17
 
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+/*
+ * npcm_i2caddr array:
+ * The module supports having multiple own slave addresses.
+ * Since the addr regs are sprinkled all over the address space,
+ * use this array to get the address or each register.
+ */
+#define I2C_NUM_OWN_ADDR 10
+const int npcm_i2caddr[I2C_NUM_OWN_ADDR] = {
+       NPCM_I2CADDR1, NPCM_I2CADDR2, NPCM_I2CADDR3, NPCM_I2CADDR4,
+       NPCM_I2CADDR5, NPCM_I2CADDR6, NPCM_I2CADDR7, NPCM_I2CADDR8,
+       NPCM_I2CADDR9, NPCM_I2CADDR10,
+};
+#endif
+
 #define NPCM_I2CCTL4                   0x1A
 #define NPCM_I2CCTL5                   0x1B
 #define NPCM_I2CSCLLT                  0x1C /* SCL Low Time */
@@ -265,6 +298,16 @@ struct npcm_i2c {
        bool read_block_use;
        unsigned long int_time_stamp;
        unsigned long bus_freq; /* in Hz */
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       u8 own_slave_addr;
+       struct i2c_client *slave;
+       int slv_rd_size;
+       int slv_rd_ind;
+       int slv_wr_size;
+       int slv_wr_ind;
+       u8 slv_rd_buf[I2C_HW_FIFO_SIZE];
+       u8 slv_wr_buf[I2C_HW_FIFO_SIZE];
+#endif
        struct dentry *debugfs; /* debugfs device directory */
        u64 ber_cnt;
        u64 rec_succ_cnt;
@@ -296,6 +339,10 @@ static void npcm_i2c_init_params(struct npcm_i2c *bus)
        bus->int_time_stamp = 0;
        bus->PEC_use = false;
        bus->PEC_mask = 0;
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       if (bus->slave)
+               bus->master_or_slave = I2C_SLAVE;
+#endif
 }
 
 static inline void npcm_i2c_wr_byte(struct npcm_i2c *bus, u8 data)
@@ -341,6 +388,18 @@ static void npcm_i2c_disable(struct npcm_i2c *bus)
 {
        u8 i2cctl2;
 
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       int i;
+
+       /* select bank 0 for I2C addresses */
+       npcm_i2c_select_bank(bus, I2C_BANK_0);
+
+       /* Slave addresses removal */
+       for (i = I2C_SLAVE_ADDR1; i < I2C_NUM_OWN_ADDR; i++)
+               iowrite8(0, bus->reg + npcm_i2caddr[i]);
+
+       npcm_i2c_select_bank(bus, I2C_BANK_1);
+#endif
        /* Disable module */
        i2cctl2 = ioread8(bus->reg + NPCM_I2CCTL2);
        i2cctl2 = i2cctl2 & ~I2CCTL2_ENABLE;
@@ -504,6 +563,61 @@ static inline void npcm_i2c_nack(struct npcm_i2c *bus)
        iowrite8(val, bus->reg + NPCM_I2CCTL1);
 }
 
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+static void npcm_i2c_slave_int_enable(struct npcm_i2c *bus, bool enable)
+{
+       u8 i2cctl1;
+
+       /* enable interrupt on slave match: */
+       i2cctl1 = ioread8(bus->reg + NPCM_I2CCTL1);
+       i2cctl1 &= ~NPCM_I2CCTL1_RWS;
+       if (enable)
+               i2cctl1 |= NPCM_I2CCTL1_NMINTE;
+       else
+               i2cctl1 &= ~NPCM_I2CCTL1_NMINTE;
+       iowrite8(i2cctl1, bus->reg + NPCM_I2CCTL1);
+}
+
+static int npcm_i2c_slave_enable(struct npcm_i2c *bus, enum i2c_addr addr_type,
+                                u8 addr, bool enable)
+{
+       u8 i2cctl1;
+       u8 i2cctl3;
+       u8 sa_reg;
+
+       sa_reg = (addr & 0x7F) | FIELD_PREP(NPCM_I2CADDR_SAEN, enable);
+       if (addr_type == I2C_GC_ADDR) {
+               i2cctl1 = ioread8(bus->reg + NPCM_I2CCTL1);
+               if (enable)
+                       i2cctl1 |= NPCM_I2CCTL1_GCMEN;
+               else
+                       i2cctl1 &= ~NPCM_I2CCTL1_GCMEN;
+               iowrite8(i2cctl1, bus->reg + NPCM_I2CCTL1);
+               return 0;
+       }
+       if (addr_type == I2C_ARP_ADDR) {
+               i2cctl3 = ioread8(bus->reg + NPCM_I2CCTL3);
+               if (enable)
+                       i2cctl3 |= I2CCTL3_ARPMEN;
+               else
+                       i2cctl3 &= ~I2CCTL3_ARPMEN;
+               iowrite8(i2cctl3, bus->reg + NPCM_I2CCTL3);
+               return 0;
+       }
+       if (addr_type >= I2C_ARP_ADDR)
+               return -EFAULT;
+       /* select bank 0 for address 3 to 10 */
+       if (addr_type > I2C_SLAVE_ADDR2)
+               npcm_i2c_select_bank(bus, I2C_BANK_0);
+       /* Set and enable the address */
+       iowrite8(sa_reg, bus->reg + npcm_i2caddr[addr_type]);
+       npcm_i2c_slave_int_enable(bus, enable);
+       if (addr_type > I2C_SLAVE_ADDR2)
+               npcm_i2c_select_bank(bus, I2C_BANK_1);
+       return 0;
+}
+#endif
+
 static void npcm_i2c_reset(struct npcm_i2c *bus)
 {
        /*
@@ -511,6 +625,9 @@ static void npcm_i2c_reset(struct npcm_i2c *bus)
         *  is disabled.
         */
        u8 i2cctl1;
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       u8 addr;
+#endif
 
        i2cctl1 = ioread8(bus->reg + NPCM_I2CCTL1);
 
@@ -531,6 +648,13 @@ static void npcm_i2c_reset(struct npcm_i2c *bus)
        /* Clear all fifo bits: */
        iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO, bus->reg + NPCM_I2CFIF_CTS);
 
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       if (bus->slave) {
+               addr = bus->slave->addr;
+               npcm_i2c_slave_enable(bus, I2C_SLAVE_ADDR1, addr, true);
+       }
+#endif
+
        bus->state = I2C_IDLE;
 }
 
@@ -596,6 +720,10 @@ static void npcm_i2c_callback(struct npcm_i2c *bus,
        }
 
        bus->operation = I2C_NO_OPER;
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       if (bus->slave)
+               bus->master_or_slave = I2C_SLAVE;
+#endif
 }
 
 static u8 npcm_i2c_fifo_usage(struct npcm_i2c *bus)
@@ -707,6 +835,459 @@ static void npcm_i2c_master_abort(struct npcm_i2c *bus)
        npcm_i2c_clear_master_status(bus);
 }
 
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+static u8 npcm_i2c_get_slave_addr(struct npcm_i2c *bus, enum i2c_addr addr_type)
+{
+       u8 slave_add;
+
+       /* select bank 0 for address 3 to 10 */
+       if (addr_type > I2C_SLAVE_ADDR2)
+               npcm_i2c_select_bank(bus, I2C_BANK_0);
+
+       slave_add = ioread8(bus->reg + npcm_i2caddr[(int)addr_type]);
+
+       if (addr_type > I2C_SLAVE_ADDR2)
+               npcm_i2c_select_bank(bus, I2C_BANK_1);
+
+       return slave_add;
+}
+
+static int npcm_i2c_remove_slave_addr(struct npcm_i2c *bus, u8 slave_add)
+{
+       int i;
+
+       /* Set the enable bit */
+       slave_add |= 0x80;
+       npcm_i2c_select_bank(bus, I2C_BANK_0);
+       for (i = I2C_SLAVE_ADDR1; i < I2C_NUM_OWN_ADDR; i++) {
+               if (ioread8(bus->reg + npcm_i2caddr[i]) == slave_add)
+                       iowrite8(0, bus->reg + npcm_i2caddr[i]);
+       }
+       npcm_i2c_select_bank(bus, I2C_BANK_1);
+       return 0;
+}
+
+static void npcm_i2c_write_fifo_slave(struct npcm_i2c *bus, u16 max_bytes)
+{
+       /*
+        * Fill the FIFO, while the FIFO is not full and there are more bytes
+        * to write
+        */
+       npcm_i2c_clear_fifo_int(bus);
+       npcm_i2c_clear_tx_fifo(bus);
+       iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
+       while (max_bytes-- && I2C_HW_FIFO_SIZE != npcm_i2c_fifo_usage(bus)) {
+               if (bus->slv_wr_size <= 0)
+                       break;
+               bus->slv_wr_ind = bus->slv_wr_ind % I2C_HW_FIFO_SIZE;
+               npcm_i2c_wr_byte(bus, bus->slv_wr_buf[bus->slv_wr_ind]);
+               bus->slv_wr_ind++;
+               bus->slv_wr_ind = bus->slv_wr_ind % I2C_HW_FIFO_SIZE;
+               bus->slv_wr_size--;
+       }
+}
+
+static void npcm_i2c_read_fifo_slave(struct npcm_i2c *bus, u8 bytes_in_fifo)
+{
+       u8 data;
+
+       if (!bus->slave)
+               return;
+
+       while (bytes_in_fifo--) {
+               data = npcm_i2c_rd_byte(bus);
+
+               bus->slv_rd_ind = bus->slv_rd_ind % I2C_HW_FIFO_SIZE;
+               bus->slv_rd_buf[bus->slv_rd_ind] = data;
+               bus->slv_rd_ind++;
+
+               /* 1st byte is length in block protocol: */
+               if (bus->slv_rd_ind == 1 && bus->read_block_use)
+                       bus->slv_rd_size = data + bus->PEC_use + 1;
+       }
+}
+
+static int npcm_i2c_slave_get_wr_buf(struct npcm_i2c *bus)
+{
+       int i;
+       u8 value;
+       int ind;
+       int ret = bus->slv_wr_ind;
+
+       /* fill a cyclic buffer */
+       for (i = 0; i < I2C_HW_FIFO_SIZE; i++) {
+               if (bus->slv_wr_size >= I2C_HW_FIFO_SIZE)
+                       break;
+               i2c_slave_event(bus->slave, I2C_SLAVE_READ_REQUESTED, &value);
+               ind = (bus->slv_wr_ind + bus->slv_wr_size) % I2C_HW_FIFO_SIZE;
+               bus->slv_wr_buf[ind] = value;
+               bus->slv_wr_size++;
+               i2c_slave_event(bus->slave, I2C_SLAVE_READ_PROCESSED, &value);
+       }
+       return I2C_HW_FIFO_SIZE - ret;
+}
+
+static void npcm_i2c_slave_send_rd_buf(struct npcm_i2c *bus)
+{
+       int i;
+
+       for (i = 0; i < bus->slv_rd_ind; i++)
+               i2c_slave_event(bus->slave, I2C_SLAVE_WRITE_RECEIVED,
+                               &bus->slv_rd_buf[i]);
+       /*
+        * once we send bytes up, need to reset the counter of the wr buf
+        * got data from master (new offset in device), ignore wr fifo:
+        */
+       if (bus->slv_rd_ind) {
+               bus->slv_wr_size = 0;
+               bus->slv_wr_ind = 0;
+       }
+
+       bus->slv_rd_ind = 0;
+       bus->slv_rd_size = bus->adap.quirks->max_read_len;
+
+       npcm_i2c_clear_fifo_int(bus);
+       npcm_i2c_clear_rx_fifo(bus);
+}
+
+static void npcm_i2c_slave_receive(struct npcm_i2c *bus, u16 nread,
+                                  u8 *read_data)
+{
+       bus->state = I2C_OPER_STARTED;
+       bus->operation = I2C_READ_OPER;
+       bus->slv_rd_size = nread;
+       bus->slv_rd_ind = 0;
+
+       iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
+       iowrite8(I2C_HW_FIFO_SIZE, bus->reg + NPCM_I2CRXF_CTL);
+       npcm_i2c_clear_tx_fifo(bus);
+       npcm_i2c_clear_rx_fifo(bus);
+}
+
+static void npcm_i2c_slave_xmit(struct npcm_i2c *bus, u16 nwrite,
+                               u8 *write_data)
+{
+       if (nwrite == 0)
+               return;
+
+       bus->state = I2C_OPER_STARTED;
+       bus->operation = I2C_WRITE_OPER;
+
+       /* get the next buffer */
+       npcm_i2c_slave_get_wr_buf(bus);
+       npcm_i2c_write_fifo_slave(bus, nwrite);
+}
+
+/*
+ * npcm_i2c_slave_wr_buf_sync:
+ * currently slave IF only supports single byte operations.
+ * in order to utilyze the npcm HW FIFO, the driver will ask for 16 bytes
+ * at a time, pack them in buffer, and then transmit them all together
+ * to the FIFO and onward to the bus.
+ * NACK on read will be once reached to bus->adap->quirks->max_read_len.
+ * sending a NACK wherever the backend requests for it is not supported.
+ * the next two functions allow reading to local buffer before writing it all
+ * to the HW FIFO.
+ */
+static void npcm_i2c_slave_wr_buf_sync(struct npcm_i2c *bus)
+{
+       int left_in_fifo;
+
+       left_in_fifo = FIELD_GET(NPCM_I2CTXF_STS_TX_BYTES,
+                                ioread8(bus->reg + NPCM_I2CTXF_STS));
+
+       /* fifo already full: */
+       if (left_in_fifo >= I2C_HW_FIFO_SIZE ||
+           bus->slv_wr_size >= I2C_HW_FIFO_SIZE)
+               return;
+
+       /* update the wr fifo index back to the untransmitted bytes: */
+       bus->slv_wr_ind = bus->slv_wr_ind - left_in_fifo;
+       bus->slv_wr_size = bus->slv_wr_size + left_in_fifo;
+
+       if (bus->slv_wr_ind < 0)
+               bus->slv_wr_ind += I2C_HW_FIFO_SIZE;
+}
+
+static void npcm_i2c_slave_rd_wr(struct npcm_i2c *bus)
+{
+       if (NPCM_I2CST_XMIT & ioread8(bus->reg + NPCM_I2CST)) {
+               /*
+                * Slave got an address match with direction bit 1 so it should
+                * transmit data. Write till the master will NACK
+                */
+               bus->operation = I2C_WRITE_OPER;
+               npcm_i2c_slave_xmit(bus, bus->adap.quirks->max_write_len,
+                                   bus->slv_wr_buf);
+       } else {
+               /*
+                * Slave got an address match with direction bit 0 so it should
+                * receive data.
+                * this module does not support saying no to bytes.
+                * it will always ACK.
+                */
+               bus->operation = I2C_READ_OPER;
+               npcm_i2c_read_fifo_slave(bus, npcm_i2c_fifo_usage(bus));
+               bus->stop_ind = I2C_SLAVE_RCV_IND;
+               npcm_i2c_slave_send_rd_buf(bus);
+               npcm_i2c_slave_receive(bus, bus->adap.quirks->max_read_len,
+                                      bus->slv_rd_buf);
+       }
+}
+
+static irqreturn_t npcm_i2c_int_slave_handler(struct npcm_i2c *bus)
+{
+       u8 val;
+       irqreturn_t ret = IRQ_NONE;
+       u8 i2cst = ioread8(bus->reg + NPCM_I2CST);
+
+       /* Slave: A NACK has occurred */
+       if (NPCM_I2CST_NEGACK & i2cst) {
+               bus->stop_ind = I2C_NACK_IND;
+               npcm_i2c_slave_wr_buf_sync(bus);
+               if (bus->fifo_use)
+                       /* clear the FIFO */
+                       iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO,
+                                bus->reg + NPCM_I2CFIF_CTS);
+
+               /* In slave write, NACK is OK, otherwise it is a problem */
+               bus->stop_ind = I2C_NO_STATUS_IND;
+               bus->operation = I2C_NO_OPER;
+               bus->own_slave_addr = 0xFF;
+
+               /*
+                * Slave has to wait for STOP to decide this is the end
+                * of the transaction. tx is not yet considered as done
+                */
+               iowrite8(NPCM_I2CST_NEGACK, bus->reg + NPCM_I2CST);
+
+               ret = IRQ_HANDLED;
+       }
+
+       /* Slave mode: a Bus Error (BER) has been identified */
+       if (NPCM_I2CST_BER & i2cst) {
+               /*
+                * Check whether bus arbitration or Start or Stop during data
+                * xfer bus arbitration problem should not result in recovery
+                */
+               bus->stop_ind = I2C_BUS_ERR_IND;
+
+               /* wait for bus busy before clear fifo */
+               iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO, bus->reg + NPCM_I2CFIF_CTS);
+
+               bus->state = I2C_IDLE;
+
+               /*
+                * in BER case we might get 2 interrupts: one for slave one for
+                * master ( for a channel which is master\slave switching)
+                */
+               if (completion_done(&bus->cmd_complete) == false) {
+                       bus->cmd_err = -EIO;
+                       complete(&bus->cmd_complete);
+               }
+               bus->own_slave_addr = 0xFF;
+               iowrite8(NPCM_I2CST_BER, bus->reg + NPCM_I2CST);
+               ret = IRQ_HANDLED;
+       }
+
+       /* A Slave Stop Condition has been identified */
+       if (NPCM_I2CST_SLVSTP & i2cst) {
+               u8 bytes_in_fifo = npcm_i2c_fifo_usage(bus);
+
+               bus->stop_ind = I2C_SLAVE_DONE_IND;
+
+               if (bus->operation == I2C_READ_OPER)
+                       npcm_i2c_read_fifo_slave(bus, bytes_in_fifo);
+
+               /* if the buffer is empty nothing will be sent */
+               npcm_i2c_slave_send_rd_buf(bus);
+
+               /* Slave done transmitting or receiving */
+               bus->stop_ind = I2C_NO_STATUS_IND;
+
+               /*
+                * Note, just because we got here, it doesn't mean we through
+                * away the wr buffer.
+                * we keep it until the next received offset.
+                */
+               bus->operation = I2C_NO_OPER;
+               bus->own_slave_addr = 0xFF;
+               i2c_slave_event(bus->slave, I2C_SLAVE_STOP, 0);
+               iowrite8(NPCM_I2CST_SLVSTP, bus->reg + NPCM_I2CST);
+               if (bus->fifo_use) {
+                       npcm_i2c_clear_fifo_int(bus);
+                       npcm_i2c_clear_rx_fifo(bus);
+                       npcm_i2c_clear_tx_fifo(bus);
+
+                       iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO,
+                                bus->reg + NPCM_I2CFIF_CTS);
+               }
+               bus->state = I2C_IDLE;
+               ret = IRQ_HANDLED;
+       }
+
+       /* restart condition occurred and Rx-FIFO was not empty */
+       if (bus->fifo_use && FIELD_GET(NPCM_I2CFIF_CTS_SLVRSTR,
+                                      ioread8(bus->reg + NPCM_I2CFIF_CTS))) {
+               bus->stop_ind = I2C_SLAVE_RESTART_IND;
+               bus->master_or_slave = I2C_SLAVE;
+               if (bus->operation == I2C_READ_OPER)
+                       npcm_i2c_read_fifo_slave(bus, npcm_i2c_fifo_usage(bus));
+               bus->operation = I2C_WRITE_OPER;
+               iowrite8(0, bus->reg + NPCM_I2CRXF_CTL);
+               val = NPCM_I2CFIF_CTS_CLR_FIFO | NPCM_I2CFIF_CTS_SLVRSTR |
+                     NPCM_I2CFIF_CTS_RXF_TXE;
+               iowrite8(val, bus->reg + NPCM_I2CFIF_CTS);
+               npcm_i2c_slave_rd_wr(bus);
+               ret = IRQ_HANDLED;
+       }
+
+       /* A Slave Address Match has been identified */
+       if (NPCM_I2CST_NMATCH & i2cst) {
+               u8 info = 0;
+
+               /* Address match automatically implies slave mode */
+               bus->master_or_slave = I2C_SLAVE;
+               npcm_i2c_clear_fifo_int(bus);
+               npcm_i2c_clear_rx_fifo(bus);
+               npcm_i2c_clear_tx_fifo(bus);
+               iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
+               iowrite8(I2C_HW_FIFO_SIZE, bus->reg + NPCM_I2CRXF_CTL);
+               if (NPCM_I2CST_XMIT & i2cst) {
+                       bus->operation = I2C_WRITE_OPER;
+               } else {
+                       i2c_slave_event(bus->slave, I2C_SLAVE_WRITE_REQUESTED,
+                                       &info);
+                       bus->operation = I2C_READ_OPER;
+               }
+               if (bus->own_slave_addr == 0xFF) {
+                       /* Check which type of address match */
+                       val = ioread8(bus->reg + NPCM_I2CCST);
+                       if (NPCM_I2CCST_MATCH & val) {
+                               u16 addr;
+                               enum i2c_addr eaddr;
+                               u8 i2ccst2;
+                               u8 i2ccst3;
+
+                               i2ccst3 = ioread8(bus->reg + NPCM_I2CCST3);
+                               i2ccst2 = ioread8(bus->reg + NPCM_I2CCST2);
+
+                               /*
+                                * the i2c module can response to 10 own SA.
+                                * check which one was addressed by the master.
+                                * repond to the first one.
+                                */
+                               addr = ((i2ccst3 & 0x07) << 7) |
+                                       (i2ccst2 & 0x7F);
+                               info = ffs(addr);
+                               eaddr = (enum i2c_addr)info;
+                               addr = npcm_i2c_get_slave_addr(bus, eaddr);
+                               addr &= 0x7F;
+                               bus->own_slave_addr = addr;
+                               if (bus->PEC_mask & BIT(info))
+                                       bus->PEC_use = true;
+                               else
+                                       bus->PEC_use = false;
+                       } else {
+                               if (NPCM_I2CCST_GCMATCH & val)
+                                       bus->own_slave_addr = 0;
+                               if (NPCM_I2CCST_ARPMATCH & val)
+                                       bus->own_slave_addr = 0x61;
+                       }
+               } else {
+                       /*
+                        *  Slave match can happen in two options:
+                        *  1. Start, SA, read (slave read without further ado)
+                        *  2. Start, SA, read, data, restart, SA, read,  ...
+                        *     (slave read in fragmented mode)
+                        *  3. Start, SA, write, data, restart, SA, read, ..
+                        *     (regular write-read mode)
+                        */
+                       if ((bus->state == I2C_OPER_STARTED &&
+                            bus->operation == I2C_READ_OPER &&
+                            bus->stop_ind == I2C_SLAVE_XMIT_IND) ||
+                            bus->stop_ind == I2C_SLAVE_RCV_IND) {
+                               /* slave tx after slave rx w/o STOP */
+                               bus->stop_ind = I2C_SLAVE_RESTART_IND;
+                       }
+               }
+
+               if (NPCM_I2CST_XMIT & i2cst)
+                       bus->stop_ind = I2C_SLAVE_XMIT_IND;
+               else
+                       bus->stop_ind = I2C_SLAVE_RCV_IND;
+               bus->state = I2C_SLAVE_MATCH;
+               npcm_i2c_slave_rd_wr(bus);
+               iowrite8(NPCM_I2CST_NMATCH, bus->reg + NPCM_I2CST);
+               ret = IRQ_HANDLED;
+       }
+
+       /* Slave SDA status is set - tx or rx */
+       if ((NPCM_I2CST_SDAST & i2cst) ||
+           (bus->fifo_use &&
+           (npcm_i2c_tx_fifo_empty(bus) || npcm_i2c_rx_fifo_full(bus)))) {
+               npcm_i2c_slave_rd_wr(bus);
+               iowrite8(NPCM_I2CST_SDAST, bus->reg + NPCM_I2CST);
+               ret = IRQ_HANDLED;
+       } /* SDAST */
+
+       return ret;
+}
+
+static int npcm_i2c_reg_slave(struct i2c_client *client)
+{
+       unsigned long lock_flags;
+       struct npcm_i2c *bus = i2c_get_adapdata(client->adapter);
+
+       bus->slave = client;
+
+       if (!bus->slave)
+               return -EINVAL;
+
+       if (client->flags & I2C_CLIENT_TEN)
+               return -EAFNOSUPPORT;
+
+       spin_lock_irqsave(&bus->lock, lock_flags);
+
+       npcm_i2c_init_params(bus);
+       bus->slv_rd_size = 0;
+       bus->slv_wr_size = 0;
+       bus->slv_rd_ind = 0;
+       bus->slv_wr_ind = 0;
+       if (client->flags & I2C_CLIENT_PEC)
+               bus->PEC_use = true;
+
+       dev_info(bus->dev, "i2c%d register slave SA=0x%x, PEC=%d\n", bus->num,
+                client->addr, bus->PEC_use);
+
+       npcm_i2c_slave_enable(bus, I2C_SLAVE_ADDR1, client->addr, true);
+       npcm_i2c_clear_fifo_int(bus);
+       npcm_i2c_clear_rx_fifo(bus);
+       npcm_i2c_clear_tx_fifo(bus);
+       npcm_i2c_slave_int_enable(bus, true);
+
+       spin_unlock_irqrestore(&bus->lock, lock_flags);
+       return 0;
+}
+
+static int npcm_i2c_unreg_slave(struct i2c_client *client)
+{
+       struct npcm_i2c *bus = client->adapter->algo_data;
+       unsigned long lock_flags;
+
+       spin_lock_irqsave(&bus->lock, lock_flags);
+       if (!bus->slave) {
+               spin_unlock_irqrestore(&bus->lock, lock_flags);
+               return -EINVAL;
+       }
+       npcm_i2c_slave_int_enable(bus, false);
+       npcm_i2c_remove_slave_addr(bus, client->addr);
+       bus->slave = NULL;
+       spin_unlock_irqrestore(&bus->lock, lock_flags);
+       return 0;
+}
+#endif /* CONFIG_I2C_SLAVE */
+
 static void npcm_i2c_master_fifo_read(struct npcm_i2c *bus)
 {
        int rcount;
@@ -1372,6 +1953,9 @@ static int __npcm_i2c_init(struct npcm_i2c *bus, struct platform_device *pdev)
        bus->state = I2C_DISABLE;
        bus->master_or_slave = I2C_SLAVE;
        bus->int_time_stamp = 0;
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       bus->slave = NULL;
+#endif
 
        ret = device_property_read_u32(&pdev->dev, "clock-frequency",
                                       &clk_freq_hz);
@@ -1401,6 +1985,12 @@ static irqreturn_t npcm_i2c_bus_irq(int irq, void *dev_id)
                if (!npcm_i2c_int_master_handler(bus))
                        return IRQ_HANDLED;
        }
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       if (bus->slave) {
+               bus->master_or_slave = I2C_SLAVE;
+               return npcm_i2c_int_slave_handler(bus);
+       }
+#endif
        return IRQ_NONE;
 }
 
@@ -1520,6 +2110,11 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                 */
                spin_lock_irqsave(&bus->lock, flags);
                bus_busy = ioread8(bus->reg + NPCM_I2CCST) & NPCM_I2CCST_BB;
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+               if (!bus_busy && bus->slave)
+                       iowrite8((bus->slave->addr & 0x7F),
+                                bus->reg + NPCM_I2CADDR1);
+#endif
                spin_unlock_irqrestore(&bus->lock, flags);
 
        } while (time_is_after_jiffies(time_left) && bus_busy);
@@ -1564,6 +2159,12 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
        if (bus->cmd_err == -EAGAIN)
                ret = i2c_recover_bus(adap);
 
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       /* reenable slave if it was enabled */
+       if (bus->slave)
+               iowrite8((bus->slave->addr & 0x7F) | NPCM_I2CADDR_SAEN,
+                        bus->reg + NPCM_I2CADDR1);
+#endif
        return bus->cmd_err;
 }
 
@@ -1572,7 +2173,8 @@ static u32 npcm_i2c_functionality(struct i2c_adapter *adap)
        return I2C_FUNC_I2C |
               I2C_FUNC_SMBUS_EMUL |
               I2C_FUNC_SMBUS_BLOCK_DATA |
-              I2C_FUNC_SMBUS_PEC;
+              I2C_FUNC_SMBUS_PEC |
+              I2C_FUNC_SLAVE;
 }
 
 static const struct i2c_adapter_quirks npcm_i2c_quirks = {
@@ -1584,6 +2186,10 @@ static const struct i2c_adapter_quirks npcm_i2c_quirks = {
 static const struct i2c_algorithm npcm_i2c_algo = {
        .master_xfer = npcm_i2c_master_xfer,
        .functionality = npcm_i2c_functionality,
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+       .reg_slave      = npcm_i2c_reg_slave,
+       .unreg_slave    = npcm_i2c_unreg_slave,
+#endif
 };
 
 /* i2c debugfs directory: used to keep health monitor of i2c devices */