linux-kernel - Re: [PATCH v4] remoteproc: core: do pm relax when in RPROC

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Date:   Thu, 13 Oct 2022 09:40:09 +0800
From:   "Aiqun(Maria) Yu" <quic_aiquny@...cinc.com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     <linux-remoteproc@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_clew@...cinc.com>
Subject: Re: [PATCH v4] remoteproc: core: do pm relax when in RPROC_OFFLINE

Hi Mathieu,

On 10/13/2022 4:43 AM, Mathieu Poirier wrote:
> Please add what has changed from one version to another, either in a cover
> letter or after the "Signed-off-by".  There are many examples on how to do that
> on the mailing list.
> 
Thx for the information, will take a note and benefit for next time.

> On Fri, Sep 16, 2022 at 03:12:31PM +0800, Maria Yu wrote:
>> RPROC_OFFLINE state indicate there is no recovery process
>> is in progress and no chance to do the pm_relax.
>> Because when recovering from crash, rproc->lock is held and
>> state is RPROC_CRASHED -> RPROC_OFFLINE -> RPROC_RUNNING,
>> and then unlock rproc->lock.
> 
> You are correct - because the lock is held rproc->state should be set to RPROC_RUNNING
> when rproc_trigger_recovery() returns.  If that is not the case then something
> went wrong.
> 
> Function rproc_stop() sets rproc->state to RPROC_OFFLINE just before returning,
> so we know the remote processor was stopped.  Therefore if rproc->state is set
> to RPROC_OFFLINE something went wrong in either request_firmware() or
> rproc_start().  Either way the remote processor is offline and the system probably
> in an unknown/unstable.  As such I don't see how calling pm_relax() can help
> things along.
> 
PROC_OFFLINE is possible that rproc_shutdown is triggered and 
successfully finished.
Even if it is multi crash rproc_crash_handler_work contention issue, and 
last rproc_trigger_recovery bailed out with only 
rproc->state==RPROC_OFFLINE, it is still worth to do pm_relax in pair.
Since the subsystem may still can be recovered with customer's next 
trigger of rproc_start, and we can make each error out path clean with 
pm resources.

> I suggest spending time understanding what leads to the failure when recovering
> from a crash and address that problem(s).
> 
In current case, the customer's information is that the issue happened 
when rproc_shutdown is triggered at similar time. So not an issue from 
error out of rproc_trigger_recovery.
> Thanks,
> Mathieu
> 
> 
>> When the state is in RPROC_OFFLINE it means separate request
>> of rproc_stop was done and no need to hold the wakeup source
>> in crash handler to recover any more.
>>
>> Signed-off-by: Maria Yu <quic_aiquny@...cinc.com>
>> ---
>>   drivers/remoteproc/remoteproc_core.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
>> index e5279ed9a8d7..6bc7b8b7d01e 100644
>> --- a/drivers/remoteproc/remoteproc_core.c
>> +++ b/drivers/remoteproc/remoteproc_core.c
>> @@ -1956,6 +1956,17 @@ static void rproc_crash_handler_work(struct work_struct *work)
>>   	if (rproc->state == RPROC_CRASHED || rproc->state == RPROC_OFFLINE) {
>>   		/* handle only the first crash detected */
>>   		mutex_unlock(&rproc->lock);
>> +		/*
>> +		 * RPROC_OFFLINE state indicate there is no recovery process
>> +		 * is in progress and no chance to have pm_relax in place.
>> +		 * Because when recovering from crash, rproc->lock is held and
>> +		 * state is RPROC_CRASHED -> RPROC_OFFLINE -> RPROC_RUNNING,
>> +		 * and then unlock rproc->lock.
>> +		 * RPROC_OFFLINE is only an intermediate state in recovery
>> +		 * process.
>> +		 */
>> +		if (rproc->state == RPROC_OFFLINE)
>> +			pm_relax(rproc->dev.parent);
>>   		return;
>>   	}
>>   
>> -- 
>> 2.7.4
>>


-- 
Thx and BRs,
Aiqun(Maria) Yu