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

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Message-Id: <3a849f4d-2cea-458a-9045-b2ae98d4293d@app.fastmail.com>
Date: Sat, 22 Mar 2025 11:25:44 +0100
From: "Sven Peter" <sven@...npeter.dev>
To: "Andi Shyti" <andi.shyti@...nel.org>
Cc: "Janne Grunau" <j@...nau.net>, "Alyssa Rosenzweig" <alyssa@...enzweig.io>,
 "Madhavan Srinivasan" <maddy@...ux.ibm.com>,
 "Michael Ellerman" <mpe@...erman.id.au>,
 "Nicholas Piggin" <npiggin@...il.com>,
 "Christophe Leroy" <christophe.leroy@...roup.eu>,
 "Naveen N Rao" <naveen@...nel.org>,
 linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, asahi@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
 linux-kernel@...r.kernel.org, "Hector Martin" <marcan@...can.st>
Subject: Re: [PATCH 2/4] i2c: pasemi: Improve error recovery

Hi Andi,

Thanks for the review! Will send a v2 after -rc1 is out.

On Thu, Mar 20, 2025, at 01:17, Andi Shyti wrote:
> 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?

Sure.

>
>> 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.

Ack.

>
>> +		status = reg_read(smbus, REG_SMSTA);
>> +	}
>
> You could use here readx_poll_timeout() here.

Yup, that should work.

>
>> +
>> +	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.

Ack.

>
>> +		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.

Ok.

>
>> +		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?

I think that can only happen if the hardware is seriously broken because
it's always supposed to set XEN. I'll make sure to catch that case in v2
though and print a separate error message similar to how the polling case
below is taken care of right now.

>
>>  		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.

Sure, will do both for v2.



Thanks,


Sven