[PATCH 7/7] i2c: nomadik: add support for I2C_XFER_V2 - detailed fault reporting

[Dmitry Guzman]

I2C_XFER_V2 is a new API that allows I2C clients to get the detailed
report in case of transmission failure. Previously, the only information
returned by I2C bus controller was the error code; there was no way to
find out how many messages or bytes in a certain message have been sent
or received until the fault condition occurred.

This commit introduces support of this feature in i2c-nomadik driver.

Signed-off-by: Dmitry Guzman <Dmitry.Guzman@xxxxxxxxxxxx>
---
 drivers/i2c/busses/i2c-nomadik.c | 37 +++++++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-nomadik.c b/drivers/i2c/busses/i2c-nomadik.c
index 9cff0c2757fafeaf809395e02a5e754570f65e08..1cf03d634fdc856dc335a58597e0fd31ab077078 100644
--- a/drivers/i2c/busses/i2c-nomadik.c
+++ b/drivers/i2c/busses/i2c-nomadik.c
@@ -197,6 +197,7 @@ struct i2c_nmk_client {
  * @stop: stop condition.
  * @xfer_wq: xfer done wait queue.
  * @result: controller propogated result.
+ * @bytes_cplt: number of bytes completed in the message that caused a fault.
  */
 struct nmk_i2c_dev {
 	struct i2c_vendor_data		*vendor;
@@ -216,6 +217,7 @@ struct nmk_i2c_dev {
 	int				stop;
 	struct wait_queue_head		xfer_wq;
 	int				result;
+	int				bytes_cplt;
 };
 
 /* controller's abort causes */
@@ -529,6 +531,8 @@ static int read_i2c(struct nmk_i2c_dev *priv, u16 flags)
 	int status = 0;
 	bool xfer_done;
 
+	priv->cli.xfer_bytes = 0;
+
 	mcr = load_i2c_mcr_reg(priv, flags);
 	writel(mcr, priv->virtbase + I2C_MCR);
 
@@ -653,6 +657,7 @@ static int nmk_i2c_xfer_one(struct nmk_i2c_dev *priv, u16 flags)
 {
 	int status;
 
+	priv->bytes_cplt = 0;
 	if (flags & I2C_M_RD) {
 		/* read operation */
 		priv->cli.operation = I2C_READ;
@@ -678,6 +683,16 @@ static int nmk_i2c_xfer_one(struct nmk_i2c_dev *priv, u16 flags)
 			status = priv->result;
 		}
 
+		if (flags & I2C_M_RD) {
+			/* For READ messages, return the number of bytes read from FIFO */
+			priv->bytes_cplt = priv->cli.xfer_bytes;
+		} else {
+			/* For WRITE messages, return the number of bytes sent on bus */
+			priv->bytes_cplt = FIELD_GET(I2C_SR_LENGTH, i2c_sr);
+			/* LENGTH value includes the last byte that has not been sent or ACKed */
+			if (priv->bytes_cplt > 0)
+				priv->bytes_cplt--;
+		}
 		init_hw(priv);
 
 		status = status ? status : priv->result;
@@ -687,10 +702,11 @@ static int nmk_i2c_xfer_one(struct nmk_i2c_dev *priv, u16 flags)
 }
 
 /**
- * nmk_i2c_xfer() - I2C transfer function used by kernel framework
+ * nmk_i2c_xfer_v2() - I2C transfer function used by kernel framework
  * @i2c_adap: Adapter pointer to the controller
  * @msgs: Pointer to data to be written.
  * @num_msgs: Number of messages to be executed
+ * @report: Pointer to transfer report to be written.
  *
  * This is the function called by the generic kernel i2c_transfer()
  * or i2c_smbus...() API calls. Note that this code is protected by the
@@ -733,14 +749,16 @@ static int nmk_i2c_xfer_one(struct nmk_i2c_dev *priv, u16 flags)
  * please use the i2c_smbus_read_i2c_block_data()
  * or i2c_smbus_write_i2c_block_data() API
  */
-static int nmk_i2c_xfer(struct i2c_adapter *i2c_adap,
-		struct i2c_msg msgs[], int num_msgs)
+static int nmk_i2c_xfer_v2(struct i2c_adapter *i2c_adap,
+		struct i2c_msg msgs[], int num_msgs,
+		struct i2c_transfer_report *report)
 {
 	int status = 0;
 	int i;
 	struct nmk_i2c_dev *priv = i2c_get_adapdata(i2c_adap);
 
 	pm_runtime_get_sync(&priv->adev->dev);
+	priv->bytes_cplt = 0;
 
 	/* setup the i2c controller */
 	setup_i2c_controller(priv);
@@ -760,10 +778,17 @@ static int nmk_i2c_xfer(struct i2c_adapter *i2c_adap,
 	pm_runtime_put_sync(&priv->adev->dev);
 
 	/* return the no. messages processed */
-	if (status)
+	if (status) {
+		report->msgs_cplt = i;
+		report->bytes_cplt = priv->bytes_cplt;
+		report->fault_msg_idx = i;
 		return status;
-	else
+	} else {
+		report->msgs_cplt = num_msgs;
+		report->bytes_cplt = 0;
+		report->fault_msg_idx = num_msgs;
 		return num_msgs;
+	}
 }
 
 /**
@@ -1014,7 +1039,7 @@ static unsigned int nmk_i2c_functionality(struct i2c_adapter *adap)
 }
 
 static const struct i2c_algorithm nmk_i2c_algo = {
-	.xfer = nmk_i2c_xfer,
+	.xfer_v2 = nmk_i2c_xfer_v2,
 	.functionality = nmk_i2c_functionality
 };
 

-- 
2.43.0