linux-kernel - Re: [PATCH v2] serial: 8250_bcm7271: Save/restore RTS in suspend/resume

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Message-ID: <a7104148-2c11-8235-9282-5731639316f5@kernel.org>
Date:   Mon, 4 Jul 2022 08:40:05 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>,
        linux-serial@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Doug Berger <opendmb@...il.com>,
        Al Cooper <alcooperx@...il.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] serial: 8250_bcm7271: Save/restore RTS in
 suspend/resume

On 29. 06. 22, 18:02, Florian Fainelli wrote:
> From: Doug Berger <opendmb@...il.com>
> 
> Commit 9cabe26e65a8 ("serial: 8250_bcm7271: UART errors after resuming
> from S2") prevented an early enabling of RTS during resume, but it did
> not actively restore the RTS state after resume.
> 
> Fixes: 9cabe26e65a8 ("serial: 8250_bcm7271: UART errors after resuming from S2")
> Signed-off-by: Doug Berger <opendmb@...il.com>
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>   drivers/tty/serial/8250/8250_bcm7271.c | 24 ++++++++++++++++++------
>   1 file changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c
> index 9b878d023dac..b9cea38c8aff 100644
> --- a/drivers/tty/serial/8250/8250_bcm7271.c
> +++ b/drivers/tty/serial/8250/8250_bcm7271.c
...
> @@ -1180,7 +1184,15 @@ static int __maybe_unused brcmuart_resume(struct device *dev)
>   		start_rx_dma(serial8250_get_port(priv->line));
>   	}
>   	serial8250_resume_port(priv->line);
> -	port->mctrl = priv->saved_mctrl;
> +
> +	if (priv->saved_mctrl & TIOCM_RTS) {
> +		/* Restore RTS */
> +		spin_lock_irqsave(&port->lock, flags);
> +		port->mctrl |= TIOCM_RTS;
> +		spin_unlock_irqrestore(&port->lock, flags);
> +		port->ops->set_mctrl(port, port->mctrl);

Calling ->set_mctrl w/o port->lock doesn't look really safe.

regards,
-- 
js
suse labs