i2c: Retry i2c operation if fails on nack'd(EC_ERROR_BUSY).

Retry count is defined by CONFIG_I2C_NACK_RETRY_COUNT.

BUG=chrome-os-partner:37494
TEST=Tested on Cyan, observed retry happens on nack'd i2c.
BRANCH=None

Signed-off-by: li feng <li1.feng@intel.com>
Change-Id: I73ed15a52335de6c5a5b647660bfe431a8238716
Reviewed-on: https://chromium-review.googlesource.com/274689
Reviewed-by: Shawn N <shawnn@chromium.org>
Commit-Queue: Divya Jyothi <divya.jyothi@intel.com>
Tested-by: Divya Jyothi <divya.jyothi@intel.com>

4 files changed, 33 insertions, 9 deletions

diff --git a/board/cyan/board.h b/board/cyan/board.h
index 30805dea96..ddbd24ba9f 100644
--- a/board/cyan/board.h
+++ b/board/cyan/board.h
@@ -79,6 +79,9 @@
 #define I2C_PORT_ACCEL		MEC1322_I2C1
 #define I2C_PORT_THERMAL	MEC1322_I2C3
 
+#undef CONFIG_I2C_NACK_RETRY_COUNT
+#define CONFIG_I2C_NACK_RETRY_COUNT 2
+
 /* power signal definitions */
 enum power_signal {
 	X86_ALL_SYS_PWRGD = 0,
diff --git a/chip/mec1322/i2c.c b/chip/mec1322/i2c.c
index df08479ab0..846bcb969e 100644
--- a/chip/mec1322/i2c.c
+++ b/chip/mec1322/i2c.c
@@ -229,6 +229,7 @@ int chip_i2c_xfer(int port, int slave_addr, const uint8_t *out, int out_size,
 	int skip = 0;
 	int bytes_to_read;
 	uint8_t reg;
+	int ret_done;
 
 	if (out_size == 0 && in_size == 0)
 		return EC_SUCCESS;
@@ -272,11 +273,13 @@ int chip_i2c_xfer(int port, int slave_addr, const uint8_t *out, int out_size,
 		}
 
 		for (i = 0; i < out_size; ++i) {
-			if (wait_byte_done(controller))
+			ret_done = wait_byte_done(controller);
+			if (ret_done)
 				goto err_chip_i2c_xfer;
 			MEC1322_I2C_DATA(controller) = out[i];
 		}
-		if (wait_byte_done(controller))
+		ret_done = wait_byte_done(controller);
+		if (ret_done)
 			goto err_chip_i2c_xfer;
 
 		/*
@@ -320,12 +323,14 @@ int chip_i2c_xfer(int port, int slave_addr, const uint8_t *out, int out_size,
 		bytes_to_read = send_stop ? in_size - 2 : in_size;
 
 		for (i = 0; i < bytes_to_read; ++i) {
-			if (wait_byte_done(controller))
+			ret_done = wait_byte_done(controller);
+			if (ret_done)
 				goto err_chip_i2c_xfer;
 			push_in_buf(&in, MEC1322_I2C_DATA(controller), skip);
 			skip = 0;
 		}
-		if (wait_byte_done(controller))
+		ret_done = wait_byte_done(controller);
+		if (ret_done)
 			goto err_chip_i2c_xfer;
 
 		if (send_stop) {
@@ -335,7 +340,8 @@ int chip_i2c_xfer(int port, int slave_addr, const uint8_t *out, int out_size,
 			 */
 			MEC1322_I2C_CTRL(controller) = CTRL_ESO | CTRL_ENI;
 			push_in_buf(&in, MEC1322_I2C_DATA(controller), skip);
-			if (wait_byte_done(controller))
+			ret_done = wait_byte_done(controller);
+			if (ret_done)
 				goto err_chip_i2c_xfer;
 
 			/* Send STOP */
@@ -362,7 +368,12 @@ err_chip_i2c_xfer:
 	/* Send STOP and return error */
 	MEC1322_I2C_CTRL(controller) = CTRL_PIN | CTRL_ESO |
 				       CTRL_STO | CTRL_ACK;
-	return EC_ERROR_UNKNOWN;
+	if (ret_done == STS_LRB)
+		return EC_ERROR_BUSY;
+	else if (ret_done == EC_ERROR_TIMEOUT)
+		return EC_ERROR_TIMEOUT;
+	else
+		return EC_ERROR_UNKNOWN;
 }
 
 int i2c_raw_get_scl(int port)
diff --git a/common/i2c.c b/common/i2c.c
index 189420c102..3975bf1927 100644
--- a/common/i2c.c
+++ b/common/i2c.c
@@ -36,8 +36,16 @@ static struct mutex port_mutex[I2C_CONTROLLER_COUNT];
 int i2c_xfer(int port, int slave_addr, const uint8_t *out, int out_size,
 	     uint8_t *in, int in_size, int flags)
 {
-	return chip_i2c_xfer(port, slave_addr, out, out_size, in,
-			     in_size, flags);
+	int i;
+	int ret = EC_SUCCESS;
+
+	for (i = 0; i <= CONFIG_I2C_NACK_RETRY_COUNT; i++) {
+		ret = chip_i2c_xfer(port, slave_addr, out, out_size, in,
+			in_size, flags);
+		if (ret != EC_ERROR_BUSY)
+			break;
+	}
+	return ret;
 }
 
 void i2c_lock(int port, int lock)
diff --git a/include/config.h b/include/config.h
index b670d748ad..b867a440ab 100644
--- a/include/config.h
+++ b/include/config.h
@@ -805,6 +805,8 @@
 #undef CONFIG_I2C_PASSTHROUGH
 #undef CONFIG_I2C_PASSTHRU_RESTRICTED
 
+/* Defines I2C operation retry count when slave nack'd(EC_ERROR_BUSY) */
+#define CONFIG_I2C_NACK_RETRY_COUNT 0
 /*
  * I2C SCL gating.
  *
@@ -1381,7 +1383,7 @@
 /* Compile chip support for the USB device controller */
 #undef CONFIG_USB
 
-/* USB device buffers and descriptors in dedicated RAM */
+/* USB device buffers and descriptors */
 #undef CONFIG_USB_RAM_ACCESS_SIZE
 #undef CONFIG_USB_RAM_ACCESS_TYPE
 #undef CONFIG_USB_RAM_BASE