Re: [PATCH v2] usb: typec: tcpm: Migrate workqueue to RT priority for processing events

[Greg Kroah-Hartman]

On Thu, Jul 23, 2020 at 07:05:51PM -0700, Badhri Jagan Sridharan wrote:
> "tReceiverResponse 15 ms Section 6.6.2
> The receiver of a Message requiring a response Shall respond
> within tReceiverResponse in order to ensure that the
> senderâs SenderResponseTimer does not expire."
> 
> When the cpu complex is busy running other lower priority
> work items, TCPM's work queue sometimes does not get scheduled
> on time to meet the above requirement from the spec.
> Moving to kthread_work apis to run with real time priority.
> Just lower than the default threaded irq priority,
> MAX_USER_RT_PRIO/2 + 1. (Higher number implies lower priority).
> 
> Further, as observed in 1ff688209e2e, moving to hrtimers to
> overcome scheduling latency while scheduling the delayed work.
> 
> TCPM has three work streams:
> 1. tcpm_state_machine
> 2. vdm_state_machine
> 3. event_work
> 
> tcpm_state_machine and vdm_state_machine both schedule work in
> future i.e. delayed. Hence each of them have a corresponding
> hrtimer, tcpm_state_machine_timer & vdm_state_machine_timer.
> 
> When work is queued right away kthread_queue_work is used.
> Else, the relevant timer is programmed and made to queue
> the kthread_work upon timer expiry.
> 
> kthread_create_worker only creates one kthread worker thread,
> hence single threadedness of workqueue is retained.
> 
> Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>

This doesn't apply against my usb-next branch at all.

Can you rebase and resend?

Remember to collect the reviewed-by tags as well when you do so.

thanks,

greg k-h