drivers: i2c: Correct i2c_dw target implementation

The I2C target implementation for i2c_dw does not follow the
zephyr target specification. The following three issues are corrected:

1) The read_requested CB is called on every byte of the transaction
    - it must be called only on the first byte of the transaction
2) The read_processed CB is called on every byte of the transaction
    - it must be called only on bytes following the first byte
3) Bytes returned in the data ptr param of read_processed are not
    sent to the controller
     -These bytes must be sent to the controller

Signed-off-by: James Growden <[email protected]>

Author: jgrowdenTT

drivers/i2c/i2c_dw.c

@@ -593,12 +593,18 @@ static void i2c_dw_isr(const struct device *port)
 			if (slave_activity) {
 				read_clr_rd_req(reg_base);
 				dw->state = I2C_DW_CMD_RECV;
-				if (slave_cb->read_requested) {
-					slave_cb->read_requested(dw->slave_cfg, &data);
-					i2c_dw_write_byte_non_blocking(port, data);
-				}
-				if (slave_cb->read_processed) {
-					slave_cb->read_processed(dw->slave_cfg, &data);
+
+				if (!dw->read_in_progress) {
+					if (slave_cb->read_requested) {
+						slave_cb->read_requested(dw->slave_cfg, &data);
+						i2c_dw_write_byte_non_blocking(port, data);
+					}
+					dw->read_in_progress = true;
+				} else {
+					if (slave_cb->read_processed) {
+						slave_cb->read_processed(dw->slave_cfg, &data);
+						i2c_dw_write_byte_non_blocking(port, data);
+					}
 				}
 			}
 		}
@@ -1125,6 +1131,7 @@ static int i2c_dw_slave_register(const struct device *dev, struct i2c_target_con
 	uint32_t reg_base = get_regs(dev);
 	int ret;
 
+	dw->read_in_progress = false;
 	dw->slave_cfg = cfg;
 	ret = i2c_dw_set_slave_mode(dev, cfg->address);
 	write_intr_mask(DW_INTR_MASK_RX_FULL | DW_INTR_MASK_RD_REQ | DW_INTR_MASK_TX_ABRT |
@@ -1188,6 +1195,7 @@ static void i2c_dw_slave_read_clear_intr_bits(const struct device *dev)
 	if (intr_stat.bits.stop_det) {
 		read_clr_stop_det(reg_base);
 		dw->state = I2C_DW_STATE_READY;
+		dw->read_in_progress = false;
 		if (slave_cb->stop) {
 			slave_cb->stop(dw->slave_cfg);
 		}

drivers/i2c/i2c_dw.h

@@ -140,6 +140,7 @@ struct i2c_dw_dev_config {
 	uint32_t request_bytes;
 	uint8_t xfr_flags;
 	bool support_hs_mode;
+	bool read_in_progress;
 #ifdef CONFIG_I2C_DW_LPSS_DMA
 	uintptr_t phy_addr;
 	uintptr_t base_addr;