linux-kernel - Re: [PATCH 3/7] i3c: master: Mark last_busy on IBI when runtime PM is allowed

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Message-ID: <aXvJTPWhQwFfv57G@lizhi-Precision-Tower-5810>
Date: Thu, 29 Jan 2026 15:55:40 -0500
From: Frank Li <Frank.li@....com>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: alexandre.belloni@...tlin.com, linux-i3c@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 3/7] i3c: master: Mark last_busy on IBI when runtime PM
 is allowed

On Thu, Jan 29, 2026 at 10:42:32PM +0200, Adrian Hunter wrote:
> On 29/01/2026 21:56, Frank Li wrote:
> > On Thu, Jan 29, 2026 at 08:18:37PM +0200, Adrian Hunter wrote:
> >> When an IBI can be received after the controller is
> >> pm_runtime_put_autosuspend()'ed, the interrupt may occur just before the
> >> device is auto‑suspended.  In such cases, the runtime PM core may not see
> >> any recent activity and may suspend the device earlier than intended.
> >>
> >> Mark the controller as last busy whenever an IBI is queued (when
> >> rpm_ibi_allowed is set) so that the auto-suspend delay correctly reflects
> >> recent bus activity and avoids premature suspension.
> >
> > look like this can't resolve problem. pm_runtime_mark_last_busy() just
> > change dev->power.last_busy. If suspend before it, nothing happen.
>
> It should be effective.
>
> rpm_suspend() recalculates the autosuspend expiry time based on
> last_busy (see pm_runtime_autosuspend_expiration()) and restarts
> the timer is it is in the future.
>
> >
> > irq use thread irq, in irq thread call pm_runtime_resume() if needs.
> >
> > And this function call by irq handle, just put to work queue, what's impact
> > if do nothing here?
>
> Just premature runtime suspension inconsistent with autosuspend_delay.


   CPU 0            CPU 1
1. rpm_suspend()    2. pm_runtime_mark_last_busy(master->rpm_dev)

if 2 happen before 1, it can extend suspend. 2 happen after 1, it should
do nothing.

Frank
>
> >
> > Frank
> >
> >>
> >> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> >> ---
> >>  drivers/i3c/master.c | 5 +++++
> >>  1 file changed, 5 insertions(+)
> >>
> >> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> >> index bcc493dc9d04..dcc07ebc50a2 100644
> >> --- a/drivers/i3c/master.c
> >> +++ b/drivers/i3c/master.c
> >> @@ -2721,9 +2721,14 @@ static void i3c_master_unregister_i3c_devs(struct i3c_master_controller *master)
> >>   */
> >>  void i3c_master_queue_ibi(struct i3c_dev_desc *dev, struct i3c_ibi_slot *slot)
> >>  {
> >> +	struct i3c_master_controller *master = i3c_dev_get_master(dev);
> >> +
> >>  	if (!dev->ibi || !slot)
> >>  		return;
> >>
> >> +	if (master->rpm_ibi_allowed)
> >> +		pm_runtime_mark_last_busy(master->rpm_dev);
> >> +
> >>  	atomic_inc(&dev->ibi->pending_ibis);
> >>  	queue_work(dev->ibi->wq, &slot->work);
> >>  }
> >> --
> >> 2.51.0
> >>
>