linux-kernel - Re: [PATCH] serial: 8250_dw: fix wrong logic in dw8250_check

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Message-ID: <1459504683.5907.151.camel@linux.intel.com>
Date:	Fri, 01 Apr 2016 12:58:03 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Noam Camus <noamc@...hip.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	guohanjun@...wei.com, xuwei5@...ilicon.com
Subject: Re: [PATCH] serial: 8250_dw: fix wrong logic in dw8250_check_lcr()

On Fri, 2016-04-01 at 17:06 +0800, Kefeng Wang wrote:
> Commit cdcea058e510("serial: 8250_dw: Avoid serial_outx code
> duplicate
> with new dw8250_check_lcr()") introduce a wrong logic when write val
> to
> LCR reg. When CONFIG_64BIT enabled, __raw_writeq is used
> unconditionally.
> 
> But for !PORT_OCTEON, we better to use coincident write func.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
> 
> We met following calltrace twice, if the change is not necessary,
> correct me,
> and any advice will be appreciated, thanks.

So, does this fix you issue? If it does than perhaps you need to Cc
stable@ and put Fixes tag as well.

> --- a/drivers/tty/serial/8250/8250_dw.c
> +++ b/drivers/tty/serial/8250/8250_dw.c
> @@ -104,15 +104,16 @@ static void dw8250_check_lcr(struct uart_port
> *p, int value)
>  		dw8250_force_idle(p);
>  
>  #ifdef CONFIG_64BIT
> -		__raw_writeq(value & 0xff, offset);
> -#else
> +		if (p->type == PORT_OCTEON)
> +			__raw_writeq(value & 0xff, offset);
> +		else
> +#endif

You may also get rid of this one, like

if (IS_ENABLED(CONFIG_64BIT) && p->type == PORT_OCTEON)
 ...
else if
...

>  		if (p->iotype == UPIO_MEM32)
>  			writel(value, offset);
>  		else if (p->iotype == UPIO_MEM32BE)
>  			iowrite32be(value, offset);
>  		else
>  			writeb(value, offset);
> -#endif
>  	}
>  	/*
>  	 * FIXME: this deadlocks if port->lock is already held

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy