i2c: pasemi: Improve timeout handling and error recovery

The hardware (supposedly) has a 25ms timeout for clock stretching, but
the driver uses a 10ms timeout, which is too low (and actually gets hit
with the tipd controllers on Apple Silicon machines sporadically).

Increase the timeout to 100ms, which should be plenty, and then add
handling for all the missing error condition, and better recovery in
pasemi_smb_clear(). Since this needs a bunch more bit defines, take
the change to switch to bitfield.h macros, which is much more readable.

Signed-off-by: Hector Martin <marcan@marcan.st>

Author: marcan

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 +131,32 @@ 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)
+		return -EBUSY;
+
+	/* Got NACK? */
+	if (status & SMSTA_MTN)
+		return -ENXIO;
+
 	/* Clear XEN */
 	reg_write(smbus, REG_SMSTA, SMSTA_XEN);
 
@@ -177,7 +217,8 @@ 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 +241,8 @@ 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: