linux-kernel - Re: [PATCHv3] serial: of-serial: fix up PM ops on no_console

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Message-ID: <543BBF02.20302@hurleysoftware.com>
Date:	Mon, 13 Oct 2014 08:01:06 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Jingchang Lu <jingchang.lu@...escale.com>,
	gregkh@...uxfoundation.org
CC:	josephl@...dia.com, arnd@...db.de, linux-serial@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3] serial: of-serial: fix up PM ops on no_console_suspend
 and port type

On 10/13/2014 05:14 AM, Jingchang Lu wrote:
> This patch fixes commit 2dea53bf57783f243c892e99c10c6921e956aa7e,
> "serial: of-serial: add PM suspend/resume support", which disables
> the uart clock on suspend, but also causes a hardware hang on register
> access if no_console_suspend command line option is used.
> 
> Also, not every of_serial device is an 8250 port, so the serial8250
> suspend/resume functions should only be applied to a real 8250 port.
> 
> Signed-off-by: Jingchang Lu <jingchang.lu@...escale.com>
> ---
> changes in v3:
>  fix up point reference and deference.
> 
> changes in v2:
>  add switch selection on uart type.
> 
>  drivers/tty/serial/of_serial.c | 42 ++++++++++++++++++++++++++++++++++++------
>  1 file changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/tty/serial/of_serial.c b/drivers/tty/serial/of_serial.c
> index 8bc2563..9d747a7 100644
> --- a/drivers/tty/serial/of_serial.c
> +++ b/drivers/tty/serial/of_serial.c
> @@ -245,9 +245,24 @@ 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)
> -		clk_disable_unprepare(info->clk);
> +	switch(info->type) {
> +#ifdef CONFIG_SERIAL_8250
> +	case PORT_8250 ... PORT_MAX_8250:
> +	{
> +		struct uart_8250_port *port8250;
> +		port8250 = serial8250_get_port(info->line);
> +
> +		serial8250_suspend_port(info->line);
> +		if (info->clk &&
> +		    (!uart_console(&port8250->port) ||
> +		    (uart_console(&port8250->port) && console_suspend_enabled)))

This conditional is the same as

		if (info->clk && (!uart_console(&port8250->port) || console_suspend_enabled))

> +			clk_disable_unprepare(info->clk);
> +		break;
> +	}
> +#endif
> +	default:
> +		break;
> +	}

I suggest you separate this into a separate function like:

#ifdef CONFIG_SERIAL_8250
static void of_serial_suspend_8250(struct of_serial_info *info)
{
	struct uart_8250_port *uart = serial_8250_get_port(info->line);
	struct uart_port *port = &uart->port;

	serial8250_suspend_port(info->line);
	if (info->clk && (!uart_console(port) || console_suspend_enabled))
		clk_disable_unprepare(info->clk);
}
#else
static inline void of_serial_suspend_8250(struct of_serial_info *info)
{ }
#endif

and call it like:

static int of_serial_suspend(struct device *dev)
{
	struct of_serial_info *info = dev_get_drvdata(dev);

	switch (info->type) {
	case PORT_8250 ... PORT_MAX_8250:
		of_serial_suspend_8250(info);
		break;
	}

	return 0;
}

I did not build-test this, so you should.

Regards,
Peter Hurley

>  
>  	return 0;
>  }
> @@ -256,10 +271,25 @@ static int of_serial_resume(struct device *dev)
>  {
>  	struct of_serial_info *info = dev_get_drvdata(dev);
>  
> -	if (info->clk)
> -		clk_prepare_enable(info->clk);
> +	switch(info->type) {
> +#ifdef CONFIG_SERIAL_8250
> +	case PORT_8250 ... PORT_MAX_8250:
> +	{
> +		struct uart_8250_port *port8250;
> +		port8250 = serial8250_get_port(info->line);
> +
> +		if (info->clk &&
> +		    (!uart_console(&port8250->port) ||
> +		    (uart_console(&port8250->port) && console_suspend_enabled)))
> +			clk_prepare_enable(info->clk);
>  
> -	serial8250_resume_port(info->line);
> +		serial8250_resume_port(info->line);
> +		break;
> +	}
> +#endif
> +	default:
> +		break;
> +	}
>  
>  	return 0;
>  }
> 

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