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

[Guenter Roeck <linux@roeck-us.net>]

On 7/29/20 8:37 PM, Badhri Jagan Sridharan wrote:
> Hi Guenter,
> 
> I see that Hans is saying that he has submitted some patch here.
> https://lore.kernel.org/lkml/65f27abc-69c8-3877-be5b-e5e478153af9@redhat.com/
> But, haven't found the actual patches yet !
> 

https://patchwork.kernel.org/project/linux-usb/list/?series=318719

Guenter

> Thanks,
> Badhri
> 
> On Wed, Jul 29, 2020 at 8:03 PM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On 7/29/20 7:28 PM, Badhri Jagan Sridharan wrote:
>>> Hi Greg,
>>>
>>> Sure just sent the new patch v3.
>>>
>>> Patch applies cleanly on my end. So wondering what I am missing.
>>
>> I expected your patch to conflict with Hans' patch series.
>> Maybe those are in a different tree/branch ?
>>
>> Guenter
>>
>>> Just in case if you are still noticing merge conflicts.
>>>
>>> Here is the git log of my local tree:
>>> 633198cd2945b7 (HEAD -> usb-next-1) usb: typec: tcpm: Migrate workqueue to RT priority for processing events
>>> fa56dd9152ef95 (origin/usb-next) Merge tag 'usb-serial-5.9-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial into usb-next
>>> 25252919a1050e xhci: dbgtty: Make some functions static
>>> b0e02550346e67 xhci: dbc: Make function xhci_dbc_ring_alloc() static
>>> ca6377900974c3 Revert "usb: dwc2: override PHY input signals with usb role switch support"
>>> 09df709cb5aeb2 Revert "usb: dwc2: don't use ID/Vbus detection if usb-role-switch on STM32MP15 SoCs"
>>> 17a82716587e9d USB: iowarrior: fix up report size handling for some devices
>>> e98ba8cc3f8a89 Merge tag 'usb-for-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb <http://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb> into usb-next
>>> c97793089b11f7 Merge 5.8-rc7 into usb-next
>>> 92ed301919932f (tag: v5.8-rc7, origin/usb-linus, origin/main) Linux 5.8-rc7
>>>
>>> Was comparing against https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/log/?h=usb-next
>>>
>>> Thanks,
>>> Badhri
>>>
>>> On Wed, Jul 29, 2020 at 7:53 AM Greg Kroah-Hartman <gregkh@linuxfoundation.org <mailto:gregkh@linuxfoundation.org>> wrote:
>>>
>>>     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
>>>     > sender’s 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@google.com <mailto:badhri@google.com>>
>>>
>>>     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
>>>
>>