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

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Message-ID: <1db7b04b-ee65-4791-8db5-0dffc7befca2@intel.com>
Date: Thu, 29 Jan 2026 22:42:32 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Frank Li <Frank.li@....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 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.

> 
> 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
>>