[PATCH 2/4] i2c: pasemi: Improve error recovery

[Sven Peter via B4 Relay]

From: Hector Martin <marcan at marcan.st>

The hardware (supposedly) has a 25ms timeout for clock stretching
and the driver uses 100ms which should be plenty. The error
reocvery itself is however lacking.

Add handling for all the missing error condition, and better recovery in
pasemi_smb_clear(). Also move the timeout to a #define since it's used
in multiple places now.

Signed-off-by: Hector Martin <marcan at marcan.st>
[sven: adjusted commit message after splitting the commit into two]
Signed-off-by: Sven Peter <sven at svenpeter.dev>
---
 drivers/i2c/busses/i2c-pasemi-core.c | 70 +++++++++++++++++++++++++++++-------
 1 file changed, 58 insertions(+), 12 deletions(-)

diff --git a/drivers/i2c/busses/i2c-pasemi-core.c b/drivers/i2c/busses/i2c-pasemi-core.c
index bd128ab2e2eb..770b86b92a10 100644
--- a/drivers/i2c/busses/i2c-pasemi-core.c
+++ b/drivers/i2c/busses/i2c-pasemi-core.c
@@ -52,6 +52,8 @@
 #define CTL_UJM		BIT(8)
 #define CTL_CLK_M	GENMASK(7, 0)
 
+#define TRANSFER_TIMEOUT_MS	100
+
 static inline void reg_write(struct pasemi_smbus *smbus, int reg, int val)
 {
 	dev_dbg(smbus->dev, "smbus write reg %x val %08x\n", reg, val);
@@ -80,23 +82,45 @@ static void pasemi_reset(struct pasemi_smbus *smbus)
 	reinit_completion(&smbus->irq_completion);
 }
 
-static void pasemi_smb_clear(struct pasemi_smbus *smbus)
+static int pasemi_smb_clear(struct pasemi_smbus *smbus)
 {
 	unsigned int status;
+	int timeout = TRANSFER_TIMEOUT_MS;
 
 	status = reg_read(smbus, REG_SMSTA);
+
+	/* First wait for the bus to go idle */
+	while ((status & (SMSTA_XIP | SMSTA_JAM)) && timeout--) {
+		msleep(1);
+		status = reg_read(smbus, REG_SMSTA);
+	}
+
+	if (timeout < 0) {
+		dev_warn(smbus->dev, "Bus is still stuck (status 0x%08x)\n", status);
+		return -EIO;
+	}
+
+	/* If any badness happened or there is data in the FIFOs, reset the FIFOs */
+	if ((status & (SMSTA_MRNE | SMSTA_JMD | SMSTA_MTO | SMSTA_TOM | SMSTA_MTN | SMSTA_MTA)) ||
+		!(status & SMSTA_MTE))
+		pasemi_reset(smbus);
+
+	/* Clear the flags */
 	reg_write(smbus, REG_SMSTA, status);
+
+	return 0;
 }
 
 static int pasemi_smb_waitready(struct pasemi_smbus *smbus)
 {
-	int timeout = 100;
+	int timeout = TRANSFER_TIMEOUT_MS;
 	unsigned int status;
 
 	if (smbus->use_irq) {
 		reinit_completion(&smbus->irq_completion);
-		reg_write(smbus, REG_IMASK, SMSTA_XEN | SMSTA_MTN);
-		wait_for_completion_timeout(&smbus->irq_completion, msecs_to_jiffies(100));
+		/* XEN should be set when a transaction terminates, whether due to error or not */
+		reg_write(smbus, REG_IMASK, SMSTA_XEN);
+		wait_for_completion_timeout(&smbus->irq_completion, msecs_to_jiffies(timeout));
 		reg_write(smbus, REG_IMASK, 0);
 		status = reg_read(smbus, REG_SMSTA);
 	} else {
@@ -107,16 +131,36 @@ static int pasemi_smb_waitready(struct pasemi_smbus *smbus)
 		}
 	}
 
-	/* Got NACK? */
-	if (status & SMSTA_MTN)
-		return -ENXIO;
+	/* Controller timeout? */
+	if (status & SMSTA_TOM) {
+		dev_warn(smbus->dev, "Controller timeout, status 0x%08x\n", status);
+		return -EIO;
+	}
 
-	if (timeout < 0) {
-		dev_warn(smbus->dev, "Timeout, status 0x%08x\n", status);
-		reg_write(smbus, REG_SMSTA, status);
+	/* Peripheral timeout? */
+	if (status & SMSTA_MTO) {
+		dev_warn(smbus->dev, "Peripheral timeout, status 0x%08x\n", status);
 		return -ETIME;
 	}
 
+	/* Still stuck in a transaction? */
+	if (status & SMSTA_XIP) {
+		dev_warn(smbus->dev, "Bus stuck, status 0x%08x\n", status);
+		return -EIO;
+	}
+
+	/* Arbitration loss? */
+	if (status & SMSTA_MTA) {
+		dev_warn(smbus->dev, "Arbitration loss, status 0x%08x\n", status);
+		return -EBUSY;
+	}
+
+	/* Got NACK? */
+	if (status & SMSTA_MTN) {
+		dev_warn(smbus->dev, "NACK, status 0x%08x\n", status);
+		return -ENXIO;
+	}
+
 	/* Clear XEN */
 	reg_write(smbus, REG_SMSTA, SMSTA_XEN);
 
@@ -177,7 +221,8 @@ static int pasemi_i2c_xfer(struct i2c_adapter *adapter,
 	struct pasemi_smbus *smbus = adapter->algo_data;
 	int ret, i;
 
-	pasemi_smb_clear(smbus);
+	if (pasemi_smb_clear(smbus))
+		return -EIO;
 
 	ret = 0;
 
@@ -200,7 +245,8 @@ static int pasemi_smb_xfer(struct i2c_adapter *adapter,
 	addr <<= 1;
 	read_flag = read_write == I2C_SMBUS_READ;
 
-	pasemi_smb_clear(smbus);
+	if (pasemi_smb_clear(smbus))
+		return -EIO;
 
 	switch (size) {
 	case I2C_SMBUS_QUICK:

-- 
2.34.1