Re: [PATCH v4 0/4] net: ethernet: ti: cpts: fix tx timestamping timeout

[David Miller]

From: Grygorii Strashko <grygorii.strashko@xxxxxx>
Date: Fri, 28 Jul 2017 17:30:01 -0500

> With the low Ethernet connection speed cpdma notification about packet
> processing can be received before CPTS TX timestamp event, which is set
> when packet actually left CPSW while cpdma notification is sent when packet
> pushed in CPSW fifo. As result, when connection is slow and CPU is fast
> enough TX timestamping is not working properly.
> Issue was discovered using timestamping tool on am57x boards with Ethernet link
> speed forced to 100M and on am335x-evm with Ethernet link speed forced to 10M.
> 
> Patch3 - This series fixes it by introducing TX SKB queue to store PTP SKBs for
> which Ethernet Transmit Event hasn't been received yet and then re-check this
> queue with new Ethernet Transmit Events by scheduling CPTS overflow
> work more often until TX SKB queue is not empty.
> 
> Patch 1,2 - As CPTS overflow work is time critical task it important to ensure
> that its scheduling is not delayed. Unfortunately, There could be significant
> delay in CPTS work schedule under high system load and on -RT which could cause
> CPTS misbehavior due to internal counter overflow and there is no way to tune
> CPTS overflow work execution policy and priority manually. The kthread_worker
> can be used instead of workqueues, as it creates separate named kthread for
> each worker and its its execution policy and priority can be configured
> using chrt tool. Instead of modifying CPTS driver itself it was proposed to
> it was proposed to add PTP auxiliary worker to the PHC subsystem [1], so
> other drivers can benefit from this feature also.
> 
> [1] https://www.spinics.net/lists/netdev/msg445392.html

Series applied to 'net', thanks.