designware_i2c: Added s/w generation of stop bit

In the newer versions of designware i2c IP there is the possibility
of configuring it with IC_EMPTYFIFO_HOLD_MASTER_EN=1, which basically
requires the s/w to generate the stop bit condition directly, as
the h/w will not automatically generate it when TX_FIFO is empty.

To avoid generation of an extra 0x0 byte sent as data, the
IC_STOP command must be sent along with the last IC_CMD.

This patch always writes bit[9] of ic_data_cmd even in the
older versions, assuming that it is a noop there.

Signed-off-by: Armando Visconti <armando.visconti@st.com>

drivers/i2c/designware_i2c.c

@@ -283,7 +283,10 @@ int i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 
 	start_time_rx = get_timer(0);
 	while (len) {
-		writel(IC_CMD, &i2c_regs_p->ic_cmd_data);
+		if (len == 1)
+			writel(IC_CMD | IC_STOP, &i2c_regs_p->ic_cmd_data);
+		else
+			writel(IC_CMD, &i2c_regs_p->ic_cmd_data);
 
 		if (readl(&i2c_regs_p->ic_status) & IC_STATUS_RFNE) {
 			*buffer++ = (uchar)readl(&i2c_regs_p->ic_cmd_data);
@@ -322,9 +325,11 @@ int i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 	start_time_tx = get_timer(0);
 	while (len) {
 		if (readl(&i2c_regs_p->ic_status) & IC_STATUS_TFNF) {
-			writel(*buffer, &i2c_regs_p->ic_cmd_data);
+			if (--len == 0)
+				writel(*buffer | IC_STOP, &i2c_regs_p->ic_cmd_data);
+			else
+				writel(*buffer, &i2c_regs_p->ic_cmd_data);
 			buffer++;
-			len--;
 			start_time_tx = get_timer(0);
 
 		} else if (get_timer(start_time_tx) > (nb * I2C_BYTE_TO)) {

drivers/i2c/designware_i2c.h

@@ -95,6 +95,7 @@ struct i2c_regs {
 
 /* i2c data buffer and command register definitions */
 #define IC_CMD			0x0100
+#define IC_STOP			0x0200
 
 /* i2c interrupt status register definitions */
 #define IC_GEN_CALL		0x0800