[U-Boot] [PATCH] I2C: Zynq: Support for 0-length register address

[Michael Burr]

> Fixed bug with alen == 0 in 'i2c_write', 'i2c_read'
Further minor corrections:
> Write 'address' register before 'data' register.
> Write 'transfer_size' register before 'address' register.

Tested:
Xilinx ZC702 eval board.
Write and read registers with addresses of length 0 and 1.

Signed-off-by: Michael Burr <michael.burr at logicpd.com>
Cc: Heiko Schocher <hs at denx.de>
Cc: Michal Simek <monstr at monstr.eu>
---
 drivers/i2c/zynq_i2c.c |   43 +++++++++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/drivers/i2c/zynq_i2c.c b/drivers/i2c/zynq_i2c.c
index ce2d23f..9cbd3e4 100644
--- a/drivers/i2c/zynq_i2c.c
+++ b/drivers/i2c/zynq_i2c.c
@@ -187,20 +187,22 @@ int i2c_read(u8 dev, uint addr, int alen, u8 *data, int length)
 	 * Temporarily disable restart (by clearing hold)
 	 * It doesn't seem to work.
 	 */
-	clrbits_le32(&zynq_i2c->control, ZYNQ_I2C_CONTROL_RW |
-		ZYNQ_I2C_CONTROL_HOLD);
+	clrbits_le32(&zynq_i2c->control, ZYNQ_I2C_CONTROL_HOLD);
 	writel(0xFF, &zynq_i2c->interrupt_status);
-	while (alen--)
-		writel(addr >> (8*alen), &zynq_i2c->data);
-	writel(dev, &zynq_i2c->address);
+	if (alen) {
+		clrbits_le32(&zynq_i2c->control, ZYNQ_I2C_CONTROL_RW);
+		writel(dev, &zynq_i2c->address);
+		while (alen--)
+			writel(addr >> (8*alen), &zynq_i2c->data);
 
-	/* Wait for the address to be sent */
-	if (!zynq_i2c_wait(ZYNQ_I2C_INTERRUPT_COMP)) {
-		/* Release the bus */
-		clrbits_le32(&zynq_i2c->control, ZYNQ_I2C_CONTROL_HOLD);
-		return -ETIMEDOUT;
+		/* Wait for the address to be sent */
+		if (!zynq_i2c_wait(ZYNQ_I2C_INTERRUPT_COMP)) {
+			/* Release the bus */
+			clrbits_le32(&zynq_i2c->control, ZYNQ_I2C_CONTROL_HOLD);
+			return -ETIMEDOUT;
+		}
+		debug("Device acked address\n");
 	}
-	debug("Device acked address\n");
 
 	setbits_le32(&zynq_i2c->control, ZYNQ_I2C_CONTROL_CLR_FIFO |
 		ZYNQ_I2C_CONTROL_RW);
@@ -244,17 +246,18 @@ int i2c_write(u8 dev, uint addr, int alen, u8 *data, int length)
 		ZYNQ_I2C_CONTROL_HOLD);
 	clrbits_le32(&zynq_i2c->control, ZYNQ_I2C_CONTROL_RW);
 	writel(0xFF, &zynq_i2c->interrupt_status);
-	while (alen--)
-		writel(addr >> (8*alen), &zynq_i2c->data);
-	/* Start the tranfer */
 	writel(dev, &zynq_i2c->address);
-	if (!zynq_i2c_wait(ZYNQ_I2C_INTERRUPT_COMP)) {
-		/* Release the bus */
-		clrbits_le32(&zynq_i2c->control, ZYNQ_I2C_CONTROL_HOLD);
-		return -ETIMEDOUT;
+	if (alen) {
+		while (alen--)
+			writel(addr >> (8*alen), &zynq_i2c->data);
+		/* Start the tranfer */
+		if (!zynq_i2c_wait(ZYNQ_I2C_INTERRUPT_COMP)) {
+			/* Release the bus */
+			clrbits_le32(&zynq_i2c->control, ZYNQ_I2C_CONTROL_HOLD);
+			return -ETIMEDOUT;
+		}
+		debug("Device acked address\n");
 	}
-
-	debug("Device acked address\n");
 	while (length--) {
 		writel(*(cur_data++), &zynq_i2c->data);
 		if (readl(&zynq_i2c->transfer_size) == ZYNQ_I2C_FIFO_DEPTH) {
-- 
1.7.9.5