i2c-bfin-twi: Add repeat start feature to avoid break of a bundle of i2c master xfer operation

 - Create a new mode TWI_I2C_MODE_REPEAT.
 - No change to smbus operation.
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

drivers/i2c/busses/i2c-bfin-twi.c

@@ -39,9 +39,10 @@
 #define POLL_TIMEOUT       (2 * HZ)
 
 /* SMBus mode*/
-#define TWI_I2C_MODE_STANDARD		0x01
-#define TWI_I2C_MODE_STANDARDSUB	0x02
-#define TWI_I2C_MODE_COMBINED		0x04
+#define TWI_I2C_MODE_STANDARD		1
+#define TWI_I2C_MODE_STANDARDSUB	2
+#define TWI_I2C_MODE_COMBINED		3
+#define TWI_I2C_MODE_REPEAT		4
 
 struct bfin_twi_iface {
 	int			irq;
@@ -58,6 +59,9 @@ struct bfin_twi_iface {
 	struct timer_list	timeout_timer;
 	struct i2c_adapter	adap;
 	struct completion	complete;
+	struct i2c_msg 		*pmsg;
+	int			msg_num;
+	int			cur_msg;
 };
 
 static struct bfin_twi_iface twi_iface;
@@ -76,12 +80,16 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface)
 		/* start receive immediately after complete sending in
 		 * combine mode.
 		 */
-		else if (iface->cur_mode == TWI_I2C_MODE_COMBINED) {
+		else if (iface->cur_mode == TWI_I2C_MODE_COMBINED)
 			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL()
 				| MDIR | RSTART);
-		} else if (iface->manual_stop)
+		else if (iface->manual_stop)
 			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL()
 				| STOP);
+		else if (iface->cur_mode == TWI_I2C_MODE_REPEAT &&
+				iface->cur_msg+1 < iface->msg_num)
+			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL()
+				| RSTART);
 		SSYNC();
 		/* Clear status */
 		bfin_write_TWI_INT_STAT(XMTSERV);
@@ -108,6 +116,11 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface)
 			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL()
 				| STOP);
 			SSYNC();
+		} else if (iface->cur_mode == TWI_I2C_MODE_REPEAT &&
+				iface->cur_msg+1 < iface->msg_num) {
+			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL()
+				| RSTART);
+			SSYNC();
 		}
 		/* Clear interrupt source */
 		bfin_write_TWI_INT_STAT(RCVSERV);
@@ -119,7 +132,7 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface)
 		bfin_write_TWI_MASTER_STAT(0x3e);
 		bfin_write_TWI_MASTER_CTL(0);
 		SSYNC();
-		iface->result = -1;
+		iface->result = -EIO;
 		/* if both err and complete int stats are set, return proper
 		 * results.
 		 */
@@ -170,6 +183,42 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface)
 			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() |
 				MEN | MDIR);
 			SSYNC();
+		} else if (iface->cur_mode == TWI_I2C_MODE_REPEAT &&
+				iface->cur_msg+1 < iface->msg_num) {
+			iface->cur_msg++;
+			iface->transPtr = iface->pmsg[iface->cur_msg].buf;
+			iface->writeNum = iface->readNum =
+				iface->pmsg[iface->cur_msg].len;
+			/* Set Transmit device address */
+			bfin_write_TWI_MASTER_ADDR(
+				iface->pmsg[iface->cur_msg].addr);
+			if (iface->pmsg[iface->cur_msg].flags & I2C_M_RD)
+				iface->read_write = I2C_SMBUS_READ;
+			else {
+				iface->read_write = I2C_SMBUS_WRITE;
+				/* Transmit first data */
+				if (iface->writeNum > 0) {
+					bfin_write_TWI_XMT_DATA8(
+						*(iface->transPtr++));
+					iface->writeNum--;
+					SSYNC();
+				}
+			}
+
+			if (iface->pmsg[iface->cur_msg].len <= 255)
+				bfin_write_TWI_MASTER_CTL(
+				iface->pmsg[iface->cur_msg].len << 6);
+			else {
+				bfin_write_TWI_MASTER_CTL(0xff << 6);
+				iface->manual_stop = 1;
+			}
+			/* remove restart bit and enable master receive */
+			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() &
+				~RSTART);
+			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() |
+				MEN | ((iface->read_write == I2C_SMBUS_READ) ?
+				MDIR : 0));
+			SSYNC();
 		} else {
 			iface->result = 1;
 			bfin_write_TWI_INT_MASK(0);
@@ -221,7 +270,6 @@ static int bfin_twi_master_xfer(struct i2c_adapter *adap,
 {
 	struct bfin_twi_iface *iface = adap->algo_data;
 	struct i2c_msg *pmsg;
-	int i, ret;
 	int rc = 0;
 
 	if (!(bfin_read_TWI_CONTROL() & TWI_ENA))
@@ -231,81 +279,76 @@ static int bfin_twi_master_xfer(struct i2c_adapter *adap,
 		yield();
 	}
 
-	ret = 0;
-	for (i = 0; rc >= 0 && i < num; i++) {
-		pmsg = &msgs[i];
-		if (pmsg->flags & I2C_M_TEN) {
-			dev_err(&(adap->dev), "i2c-bfin-twi: 10 bits addr "
-				"not supported !\n");
-			rc = -EINVAL;
-			break;
-		}
+	iface->pmsg = msgs;
+	iface->msg_num = num;
+	iface->cur_msg = 0;
 
-		iface->cur_mode = TWI_I2C_MODE_STANDARD;
-		iface->manual_stop = 0;
-		iface->transPtr = pmsg->buf;
-		iface->writeNum = iface->readNum = pmsg->len;
-		iface->result = 0;
-		iface->timeout_count = 10;
-		/* Set Transmit device address */
-		bfin_write_TWI_MASTER_ADDR(pmsg->addr);
-
-		/* FIFO Initiation. Data in FIFO should be
-		 *  discarded before start a new operation.
-		 */
-		bfin_write_TWI_FIFO_CTL(0x3);
-		SSYNC();
-		bfin_write_TWI_FIFO_CTL(0);
-		SSYNC();
+	pmsg = &msgs[0];
+	if (pmsg->flags & I2C_M_TEN) {
+		dev_err(&adap->dev, "10 bits addr not supported!\n");
+		return -EINVAL;
+	}
 
-		if (pmsg->flags & I2C_M_RD)
-			iface->read_write = I2C_SMBUS_READ;
-		else {
-			iface->read_write = I2C_SMBUS_WRITE;
-			/* Transmit first data */
-			if (iface->writeNum > 0) {
-				bfin_write_TWI_XMT_DATA8(*(iface->transPtr++));
-				iface->writeNum--;
-				SSYNC();
-			}
+	iface->cur_mode = TWI_I2C_MODE_REPEAT;
+	iface->manual_stop = 0;
+	iface->transPtr = pmsg->buf;
+	iface->writeNum = iface->readNum = pmsg->len;
+	iface->result = 0;
+	iface->timeout_count = 10;
+	/* Set Transmit device address */
+	bfin_write_TWI_MASTER_ADDR(pmsg->addr);
+
+	/* FIFO Initiation. Data in FIFO should be
+	 *  discarded before start a new operation.
+	 */
+	bfin_write_TWI_FIFO_CTL(0x3);
+	SSYNC();
+	bfin_write_TWI_FIFO_CTL(0);
+	SSYNC();
+
+	if (pmsg->flags & I2C_M_RD)
+		iface->read_write = I2C_SMBUS_READ;
+	else {
+		iface->read_write = I2C_SMBUS_WRITE;
+		/* Transmit first data */
+		if (iface->writeNum > 0) {
+			bfin_write_TWI_XMT_DATA8(*(iface->transPtr++));
+			iface->writeNum--;
+			SSYNC();
 		}
+	}
 
-		/* clear int stat */
-		bfin_write_TWI_INT_STAT(MERR|MCOMP|XMTSERV|RCVSERV);
+	/* clear int stat */
+	bfin_write_TWI_INT_STAT(MERR | MCOMP | XMTSERV | RCVSERV);
 
-		/* Interrupt mask . Enable XMT, RCV interrupt */
-		bfin_write_TWI_INT_MASK(MCOMP | MERR |
-			((iface->read_write == I2C_SMBUS_READ)?
-			RCVSERV : XMTSERV));
-		SSYNC();
+	/* Interrupt mask . Enable XMT, RCV interrupt */
+	bfin_write_TWI_INT_MASK(MCOMP | MERR | RCVSERV | XMTSERV);
+	SSYNC();
 
-		if (pmsg->len > 0 && pmsg->len <= 255)
-			bfin_write_TWI_MASTER_CTL(pmsg->len << 6);
-		else if (pmsg->len > 255) {
-			bfin_write_TWI_MASTER_CTL(0xff << 6);
-			iface->manual_stop = 1;
-		} else
-			break;
+	if (pmsg->len <= 255)
+		bfin_write_TWI_MASTER_CTL(pmsg->len << 6);
+	else {
+		bfin_write_TWI_MASTER_CTL(0xff << 6);
+		iface->manual_stop = 1;
+	}
 
-		iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
-		add_timer(&iface->timeout_timer);
+	iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
+	add_timer(&iface->timeout_timer);
 
-		/* Master enable */
-		bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() | MEN |
-			((iface->read_write == I2C_SMBUS_READ) ? MDIR : 0) |
-			((CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ>100) ? FAST : 0));
-		SSYNC();
+	/* Master enable */
+	bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() | MEN |
+		((iface->read_write == I2C_SMBUS_READ) ? MDIR : 0) |
+		((CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ > 100) ? FAST : 0));
+	SSYNC();
 
-		wait_for_completion(&iface->complete);
+	wait_for_completion(&iface->complete);
 
-		rc = iface->result;
-		if (rc == 1)
-			ret++;
-		else if (rc == -1)
-			break;
-	}
+	rc = iface->result;
 
-	return ret;
+	if (rc == 1)
+		return num;
+	else
+		return rc;
 }
 
 /*