From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751090AbbJWMp6 (ORCPT ); Fri, 23 Oct 2015 08:45:58 -0400 Received: from mail-qk0-f181.google.com ([209.85.220.181]:36499 "EHLO mail-qk0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751115AbbJWMp4 (ORCPT ); Fri, 23 Oct 2015 08:45:56 -0400 Subject: Re: [PATCH] serial: 8250_early: do not save and restore IER in write callback To: Masahiro Yamada , linux-serial@vger.kernel.org References: <1445502100-10860-1-git-send-email-yamada.masahiro@socionext.com> Cc: Vineet Gupta , Kevin Cernekee , Jiri Slaby , Rob Herring , linux-kernel@vger.kernel.org, Eddie Huang , Greg Kroah-Hartman From: Peter Hurley Message-ID: <562A2C01.4070006@hurleysoftware.com> Date: Fri, 23 Oct 2015 08:45:53 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <1445502100-10860-1-git-send-email-yamada.masahiro@socionext.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/22/2015 04:21 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. > > Let wait_for_xmitr() melt into serial_putc(). Both of these changes are ok with me, but please split this into 2 patches so reverting either one in case of regression is trivial. Regards, Peter Hurley > Signed-off-by: Masahiro Yamada > --- > > drivers/tty/serial/8250/8250_early.c | 20 ++------------------ > 1 file changed, 2 insertions(+), 18 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c > index 7aff3d8..19aca19 100644 > --- a/drivers/tty/serial/8250/8250_early.c > +++ b/drivers/tty/serial/8250/8250_early.c > @@ -76,21 +76,17 @@ static void __init serial8250_early_out(struct uart_port *port, int offset, int > > #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) > > -static void __init wait_for_xmitr(struct uart_port *port) > +static void __init serial_putc(struct uart_port *port, int c) > { > unsigned int status; > > for (;;) { > status = serial8250_early_in(port, UART_LSR); > if ((status & BOTH_EMPTY) == BOTH_EMPTY) > - return; > + break; > cpu_relax(); > } > -} > > -static void __init serial_putc(struct uart_port *port, int c) > -{ > - wait_for_xmitr(port); > serial8250_early_out(port, UART_TX, c); > } > > @@ -99,20 +95,8 @@ 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); > - > - if (ier) > - serial8250_early_out(port, UART_IER, ier); > } > > static void __init init_port(struct earlycon_device *device) >