Re: [PATCH] ns16550: ensure polling timer is disarmed

[dmkhn@proton.me]

On Thu, Jul 31, 2025 at 08:54:10AM +0200, Jan Beulich wrote:
> On 30.07.2025 20:31, dmkhn@proton.me wrote:
> > On Wed, Jul 30, 2025 at 10:12:54AM +0200, Jan Beulich wrote:
> >> On 30.07.2025 05:13, dmkhn@proton.me wrote:
> >>> From: Denis Mukhin <dmukhin@ford.com>
> >>>
> >>> As it stands, polling timer is kept in the list of timers even after the
> >>> interrupts have been enabled / polling disabled on ns16550-compatible UART.
> >>>
> >>> Ensure polling timer is removed from the timer list once UART interrupts are
> >>> enabled.
> >>>
> >>> Signed-off-by: Denis Mukhin <dmukhin@ford.com>
> >>
> >> Wasn't it Andrew(?) who suggested something along these lines? That would
> >> want reflecting by a tag then.
> >
> > Yes, indeed.
> >
> >>
> >> Also, what's the real problem you want to solve here? The timer function
> >> would be run one more time after ->intr_works is set, and then the timer
> >> will be permanently inactive (up to a possible S3 resume). Is it being on
> >> an inactive list an actual problem? (IOW I'd like to understand if the
> >> change is merely cosmetic, or if there is some actual benefit.)
> >
> > My understanding is running polling timer one more time after the interrupts
> > are enabled is the issue: if there's a pending timer when it is known the
> > timer not needed, then the timer should be canceled.
> 
> And the effort of canceling outweighs the one extra running of the timer?

I think so, because intr_works will not flip at run-time once set.
If so, no need to keep the timer ready to be rearmed.

> 
> Jan