[PATCH v2 04/12] i2c: nomadik: return proper fault codes

[Dmitry Guzman <Dmitry.Guzman@mobileye.com>]

I2C documentation Documentation/i2c/fault-codes.rst defines fault codes
for different negative results in I2C transmittion. Previously,
i2c-nomadik driver didn't implement them properly - it returned
ETIMEDOUT on most errors and EIO on master arbitration lost.

To comply with the documentation, return the proper fault codes for
different conditions, namely:

- EAGAIN if arbitration lost
- EOVERFLOW if message is too long (>2047 bytes)
- ENXIO if target address is not acknowledged
- EIO on other errors detected by controller (for example, NACK on data)
- ETIMEDOUT if driver gets timeout waiting for message completion
  without any fault condition detected by the controller (for example,
too long message, or SDA/SCL line stuck on 0).

Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Dmitry Guzman <Dmitry.Guzman@mobileye.com>
---
 drivers/i2c/busses/i2c-nomadik.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-nomadik.c b/drivers/i2c/busses/i2c-nomadik.c
index ca9366e09e7125b9c86dd0f995162018df56634d..a3cef4b66190a9e45898e25867a3ceefce5d3d0a 100644
--- a/drivers/i2c/busses/i2c-nomadik.c
+++ b/drivers/i2c/busses/i2c-nomadik.c
@@ -226,6 +226,18 @@ static const char *abort_causes[] = {
 	"overflow, maxsize is 2047 bytes",
 };
 
+/* Linux fault codes for controller abort causes */
+static int fault_codes[] = {
+	ENXIO,
+	EIO,
+	EIO,
+	EAGAIN,
+	EIO,
+	EIO,
+	EOVERFLOW,
+	EIO
+};
+
 static inline void i2c_set_bit(void __iomem *reg, u32 mask)
 {
 	writel(readl(reg) | mask, reg);
@@ -653,6 +665,8 @@ static int nmk_i2c_xfer_one(struct nmk_i2c_dev *priv, u16 flags)
 				cause >= ARRAY_SIZE(abort_causes) ?
 				"unknown reason" :
 				abort_causes[cause]);
+			priv->result = -fault_codes[cause];
+			status = priv->result;
 		}
 
 		init_hw(priv);
@@ -865,7 +879,7 @@ static irqreturn_t i2c_irq_handler(int irq, void *arg)
 
 	/* Master Arbitration lost interrupt */
 	case I2C_IT_MAL:
-		priv->result = -EIO;
+		priv->result = -EAGAIN;
 		init_hw(priv);
 
 		i2c_set_bit(priv->virtbase + I2C_ICR, I2C_IT_MAL);

-- 
2.43.0