linux-kernel - Re: [PATCH 3/3] serial: 8250: omap: restore registers on shutdown

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Date:	Thu, 30 Jul 2015 20:51:10 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	John Ogness <john.ogness@...utronix.de>
CC:	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tony Lindgren <tony@...mide.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-omap@...r.kernel.org, nsekhar@...com, nm@...com,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH 3/3] serial: 8250: omap: restore registers on shutdown

Hi John,

On 07/30/2015 06:54 PM, John Ogness wrote:
> If DMA is active during a shutdown, a delayed restore of the
> registers may be pending. The restore must be performed after
> the DMA is stopped, otherwise the delayed restore remains
> pending and will fire upon the first DMA TX complete of a
> totally different serial session.
> 
> Signed-off-by: John Ogness <john.ogness@...utronix.de>
> ---
>  drivers/tty/serial/8250/8250_omap.c |    8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
> index 5b39892..25f6255 100644
> --- a/drivers/tty/serial/8250/8250_omap.c
> +++ b/drivers/tty/serial/8250/8250_omap.c
> @@ -657,9 +657,15 @@ static void omap_8250_shutdown(struct uart_port *port)
>  	up->ier = 0;
>  	serial_out(up, UART_IER, 0);
>  
> -	if (up->dma)
> +	if (up->dma) {
>  		serial8250_release_dma(up);
>  
> +		if (priv->delayed_restore) {
> +			priv->delayed_restore = 0;
> +			omap8250_restore_regs(up);
> +		}

I was never really a fan of the deferred set_termios();
I think it's more appropriate to wait for tx dma to
complete in omap_8250_set_termios().

Regards,
Peter Hurley


> +	}
> +
>  	/*
>  	 * Disable break condition and FIFOs
>  	 */
> 

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