[Intel-wired-lan] [PATCH net v1] ice: fix PTP stale Tx timestamps cleanup

[Paul Menzel]

Dear Michal,


Am 19.04.22 um 15:27 schrieb Michalik, Michal:

[…]

> Much thanks for your kind review of my first community patch.

Hah, I didn’t know. Congratulations, and I hope, it’s the first of many 
more to come. ;-)

> Please excuse me for a delay in answering - Monday 18th was a Public
> Holiday here in Poland.

No problem. Luckily email is async, and it’s no problem if replies only 
come after days/weeks. By the way, Easter Monday is also a public 
holiday in Germany.

>> -----Original Message-----
>> From: Paul Menzel <pmenzel at molgen.mpg.de>
>> Sent: Friday, April 15, 2022 6:37 PM

[…]

>> Am 14.04.22 um 12:23 schrieb Michal Michalik:
>>> Read stale PTP Tx timestamps from PHY on cleanup.
>>>
>>> After running out of Tx timestamps request handlers hardware (HW) stops
>>> reporting finished requests. Function ice_ptp_tx_tstamp_cleanup() used
>>> to only cleanup stale handlers in driver and was leaving the hardware
>>
>> Nit: clean up
> 
> Good catch - I should have used verb instead of noun. Will fix it in v2.
> 
>>
>>> registers not read. Not reading stale PTP Tx timestamps prevents next
>>> interrupts from arriving and makes timestamping not usable.
>>
>> Nit: unusable
> 
> Thanks - lesson learned. Will fix it in v2.

Both variants work, unusable is just a little shorter.

>> Do you have a method, how to force the network device to run out of
>> timestamps request handlers?
> 
> Unlucky - I don't have anything convenient. Both reproducing this bug
> and proving fix for it is working correctly was done by performing
> stability tests for multiple hours (using linuxptp project).

Understood. Maybe just add that as a comment in the commit message.

>>> Fixes: ea9b847cda64 ("ice: enable transmit timestamps for E810 devices")
>>> Signed-off-by: Michal Michalik <michal.michalik at intel.com>
>>> Reviewed-by: Jacob Keller <jacob.e.keller at intel.com>
>>> ---
>>>    drivers/net/ethernet/intel/ice/ice_ptp.c | 9 +++++++--
>>>    1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/intel/ice/ice_ptp.c b/drivers/net/ethernet/intel/ice/ice_ptp.c
>>> index a1cd332..826a508 100644
>>> --- a/drivers/net/ethernet/intel/ice/ice_ptp.c
>>> +++ b/drivers/net/ethernet/intel/ice/ice_ptp.c
>>> @@ -2287,6 +2287,7 @@ ice_ptp_init_tx_e810(struct ice_pf *pf, struct ice_ptp_tx *tx)
>>>    
>>>    /**
>>>     * ice_ptp_tx_tstamp_cleanup - Cleanup old timestamp requests that got dropped
>>> + * @hw: pointer to the hw struct
>>>     * @tx: PTP Tx tracker to clean up
>>>     *
>>>     * Loop through the Tx timestamp requests and see if any of them have been
>>> @@ -2295,7 +2296,7 @@ ice_ptp_init_tx_e810(struct ice_pf *pf, struct ice_ptp_tx *tx)
>>>     * timestamp will never be captured. This might happen if the packet gets
>>>     * discarded before it reaches the PHY timestamping block.
>>>     */
>>> -static void ice_ptp_tx_tstamp_cleanup(struct ice_ptp_tx *tx)
>>> +static void ice_ptp_tx_tstamp_cleanup(struct ice_hw *hw, struct ice_ptp_tx *tx)
>>>    {
>>>    	u8 idx;
>>>    
>>> @@ -2304,11 +2305,15 @@ static void ice_ptp_tx_tstamp_cleanup(struct ice_ptp_tx *tx)
>>>    
>>>    	for_each_set_bit(idx, tx->in_use, tx->len) {
>>>    		struct sk_buff *skb;
>>> +		u64 raw_tstamp;
>>>    
>>>    		/* Check if this SKB has been waiting for too long */
>>>    		if (time_is_after_jiffies(tx->tstamps[idx].start + 2 * HZ))
>>>    			continue;
>>>    
>>> +		ice_read_phy_tstamp(hw, tx->quad, idx + tx->quad_offset,
>>> +				    &raw_tstamp);
>>> +
>>
>> Are compilers or code analyzer going to complain, that nothing will be
>> done with `raw_tstamp`? Is there some attribute, that it’s unused? Maybe
>> also add a comment, this is just to read the value, and it’s not going
>> to be used.
>>
> 
> I haven't noticed any complaints from compiler. This function is used
> in different places, where all parameters are used. Do you think we
> should consider changing ice_read_phy_tstamp() so it would be able to
> accept tstamp equal to NULL and remove this unused raw_tstamp from
> here? If we leave it as is I will add a comment, according to your
> suggestion.

I guess the comment is fine, and let’s see if compilers or analyzers are 
going to complain.

>>>    		spin_lock(&tx->lock);
>>>    		skb = tx->tstamps[idx].skb;
>>>    		tx->tstamps[idx].skb = NULL;
>>> @@ -2330,7 +2335,7 @@ static void ice_ptp_periodic_work(struct kthread_work *work)
>>>    
>>>    	ice_ptp_update_cached_phctime(pf);
>>>    
>>> -	ice_ptp_tx_tstamp_cleanup(&pf->ptp.port.tx);
>>> +	ice_ptp_tx_tstamp_cleanup(&pf->hw, &pf->ptp.port.tx);
>>>    
>>>    	/* Run twice a second */
>>>    	kthread_queue_delayed_work(ptp->kworker, &ptp->work,
>>
>> Reviewed-by: Paul Menzel <pmenzel at molgen.mpg.de>


Kind regards,

Paul