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

Hi Sven,

On Sat, Feb 22, 2025 at 01:38:34PM +0000, Sven Peter via B4 Relay wrote:

The hardware (supposedly) has a 25ms timeout for clock stretching
and the driver uses 100ms which should be plenty.

Can we add this lines as a comment to the define you are adding?

The error
reocvery itself is however lacking.

...

-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);

Please, use usleep_range for 1 millisecond timeout.

+		status = reg_read(smbus, REG_SMSTA);
+	}

You could use here readx_poll_timeout() here.

+
+	if (timeout < 0) {
+		dev_warn(smbus->dev, "Bus is still stuck (status 0x%08x)\n", status);

if it's an error, please use an error.

+		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))

Please, fixe the alignment here.

+		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));

what happens if the timeout expires?

 		reg_write(smbus, REG_IMASK, 0);
 		status = reg_read(smbus, REG_SMSTA);
 	} else {

...

 	struct pasemi_smbus *smbus = adapter->algo_data;
 	int ret, i;
 
-	pasemi_smb_clear(smbus);
+	if (pasemi_smb_clear(smbus))
+		return -EIO;

Can we use

	ret = ...
	if (ret)
		return ret;

This way we return whatever comes from pasemi_smb_clear().

 
 	ret = 0;

This way we can remove this line, as well.

Andi