linux-kernel - Re: [RFC PATCH] mailbox: omap-mailbox: Flush out pending msgs before entering suspend

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Message-ID: <40726a57-35a9-450d-ba0f-879313f60732@ti.com>
Date: Wed, 22 Oct 2025 11:07:59 -0500
From: Andrew Davis <afd@...com>
To: Beleswar Padhi <b-padhi@...com>, <jassisinghbrar@...il.com>,
        <linux-kernel@...r.kernel.org>
CC: <hiagofranco@...il.com>, <hnagalla@...com>, <u-kumar1@...com>
Subject: Re: [RFC PATCH] mailbox: omap-mailbox: Flush out pending msgs before
 entering suspend

On 10/22/25 5:20 AM, Beleswar Padhi wrote:
> There may be pending messages in the mailbox FIFO that are not consumed
> by the remote processor for various reasons; the remote processor may
> already be powered off or may be in a bad state. Instead of aborting
> suspend because of these pending messages, flush the FIFOs and proceed
> with suspend. Pending messages could also be restored in the resume
> context, but since remote processors are typically rebooted during
> suspend/resume today, there is no point in restoring stale messages.
> 
> Signed-off-by: Beleswar Padhi <b-padhi@...com>
> ---
>   drivers/mailbox/omap-mailbox.c | 11 ++++-------
>   1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/mailbox/omap-mailbox.c b/drivers/mailbox/omap-mailbox.c
> index 680243751d62..5e6373911630 100644
> --- a/drivers/mailbox/omap-mailbox.c
> +++ b/drivers/mailbox/omap-mailbox.c
> @@ -341,13 +341,10 @@ static int omap_mbox_suspend(struct device *dev)
>   	if (pm_runtime_status_suspended(dev))
>   		return 0;
>   
> -	for (fifo = 0; fifo < mdev->num_fifos; fifo++) {
> -		if (mbox_read_reg(mdev, MAILBOX_MSGSTATUS(fifo))) {
> -			dev_err(mdev->dev, "fifo %d has unexpected unread messages\n",
> -				fifo);
> -			return -EBUSY;
> -		}
> -	}
> +	/* Flush out pending mbox messages before entering suspend */
> +	for (fifo = 0; fifo < mdev->num_fifos; fifo++)
> +		while (mbox_read_reg(mdev, MAILBOX_MSGSTATUS(fifo)) != 0)
> +			mbox_read_reg(mdev, MAILBOX_MESSAGE(fifo));

I'm still not convinced just throwing out messages is the correct thing
to do here, but for now at very least let's print some warning here when
messages get zapped.

Andrew

>   
>   	for (usr = 0; usr < mdev->num_users; usr++) {
>   		reg = MAILBOX_IRQENABLE(mdev->intr_type, usr);