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

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Message-ID: <20221012204344.GA1178915@p14s>
Date:   Wed, 12 Oct 2022 14:43:44 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Maria Yu <quic_aiquny@...cinc.com>
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

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.

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.  

I suggest spending time understanding what leads to the failure when recovering
from a crash and address that problem(s).

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
>