linux-kernel - RE: [PATCH] serial: of-serial: fix up PM ops on no_console

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Date:	Sat, 11 Oct 2014 03:37:26 +0000
From:	Jingchang Lu <jingchang.lu@...escale.com>
To:	Peter Hurley <peter@...leysoftware.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:	"arnd@...db.de" <arnd@...db.de>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Joseph Lo <josephl@...dia.com>
Subject: RE: [PATCH] serial: of-serial: fix up PM ops on no_console_suspend

>-----Original Message-----
>From: Peter Hurley [mailto:peter@...leysoftware.com]
>Sent: Friday, October 10, 2014 7:39 PM
>To: Lu Jingchang-B35083; gregkh@...uxfoundation.org
>Cc: arnd@...db.de; linux-serial@...r.kernel.org; linux-arm-
>kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; Joseph Lo
>Subject: Re: [PATCH] serial: of-serial: fix up PM ops on
>no_console_suspend
>
>Hi Jingchang,
>
>On 10/09/2014 05:10 AM, Jingchang Lu wrote:
>> Mandatorily disabling the uart clock will cause register access hung
>> on "no_console_suspend". This patch add condition check on it and only
>> disable the clock with console_suspend_enabled true.
>>
>> Signed-off-by: Joseph Lo <josephl@...dia.com>
>> Signed-off-by: Jingchang Lu <jingchang.lu@...escale.com>
>> ---
>>  drivers/tty/serial/of_serial.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/tty/serial/of_serial.c
>> b/drivers/tty/serial/of_serial.c index 8bc2563..a765399 100644
>> --- a/drivers/tty/serial/of_serial.c
>> +++ b/drivers/tty/serial/of_serial.c
>> @@ -246,7 +246,7 @@ static int of_serial_suspend(struct device *dev)
>>  	struct of_serial_info *info = dev_get_drvdata(dev);
>>
>>  	serial8250_suspend_port(info->line);
>> -	if (info->clk)
>> +	if (info->clk && console_suspend_enabled)
>>  		clk_disable_unprepare(info->clk);
>
>This needs to check that _this_ port is the console port, like:
>
>	if (info->clk && uart_console(port) && and console_suspend_enabled)
>		clk_disable_unprepare(info->clk);
>
>which means you need something like:
>
>	struct uart_8250_port *uart = serial8250_get_port(info->line);
>	struct uart_port *port = &uart->port;
>
>Also, there's another problem with your original patch:
>not every of_serial device is an 8250, right?
>serial8250_suspend_port() on a port that's not registered with 8250 core
>is probably going to blow up.
>
>Which means the body of of_platform_suspend() and of_platform_resume()
>should probably look like
>
>	switch (info->type) {
>#ifdef CONFIG_SERIAL_8250
>	case PORT_8250 ... PORT_MAX_8250:
>	{
>		/* current body of function */
>	}
>#endif
>	default:
>	}
>
Yes, this should be considered, then serial8250_get_port(info->line) for uart_console() also
should be put in this type switch,  Thanks.

Best Regards,
Jingchang

>Regards,
>Peter Hurley
>
>
>>
>>  	return 0;
>> @@ -256,7 +256,7 @@ static int of_serial_resume(struct device *dev)  {
>>  	struct of_serial_info *info = dev_get_drvdata(dev);
>>
>> -	if (info->clk)
>> +	if (info->clk && console_suspend_enabled)
>>  		clk_prepare_enable(info->clk);
>>
>>  	serial8250_resume_port(info->line);
>>