linux-kernel - Re: [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback

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Date:	Tue, 27 Oct 2015 09:54:34 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	linux-serial@...r.kernel.org
Cc:	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Kevin Cernekee <cernekee@...il.com>,
	Jiri Slaby <jslaby@...e.com>, Rob Herring <robh@...nel.org>,
	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in
 write callback

Hi Masahiro,

On 10/24/2015 12:17 AM, Masahiro Yamada wrote:
> The IER has already been masked in early_serial8250_setup(), there is
> no reason to save and restore it every time early_serial8250_write()
> is called.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 
>  drivers/tty/serial/8250/8250_early.c | 12 ------------
>  1 file changed, 12 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
> index 7aff3d8..559b681 100644
> --- a/drivers/tty/serial/8250/8250_early.c
> +++ b/drivers/tty/serial/8250/8250_early.c
> @@ -99,20 +99,8 @@ static void __init early_serial8250_write(struct console *console,
>  {
>  	struct earlycon_device *device = console->data;
>  	struct uart_port *port = &device->port;
> -	unsigned int ier;
> -
> -	/* Save the IER and disable interrupts preserving the UUE bit */
> -	ier = serial8250_early_in(port, UART_IER);
> -	if (ier)
> -		serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
>  
>  	uart_console_write(port, s, count, serial_putc);



> -
> -	/* Wait for transmitter to become empty and restore the IER */
> -	wait_for_xmitr(port);

This wait_for_xmitr() change needs to be in patch 2/2.

Regards,
Peter Hurley

> -
> -	if (ier)
> -		serial8250_early_out(port, UART_IER, ier);
>  }
>  
>  static void __init init_port(struct earlycon_device *device)
> 

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