Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751536AbdIKJwh (ORCPT ); Mon, 11 Sep 2017 05:52:37 -0400 Received: from mail-io0-f174.google.com ([209.85.223.174]:36422 "EHLO mail-io0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbdIKJwd (ORCPT ); Mon, 11 Sep 2017 05:52:33 -0400 X-Google-Smtp-Source: AOwi7QBwE7SEhp7nN3KLRdj9Odnxl4WHMxQ7WbayCtUdRcb1QKDhb8LwK6WDYr9lrY81HqNNpXuB4J/pmZRNFG2fIJU= MIME-Version: 1.0 In-Reply-To: <20170908153604.28383-11-romain.izard.pro@gmail.com> References: <20170908153604.28383-1-romain.izard.pro@gmail.com> <20170908153604.28383-11-romain.izard.pro@gmail.com> From: Romain Izard Date: Mon, 11 Sep 2017 11:52:12 +0200 X-Google-Sender-Auth: fbg3wLgAXM8aSFC80ZhGE9IZhRs Message-ID: Subject: Re: [PATCH v1 10/10] tty/serial: atmel: Prevent a warning on suspend To: Nicolas Ferre , Boris Brezillon , Michael Turquette , Stephen Boyd , Ludovic Desroches , Jonathan Cameron , Wenyou Yang , Josh Wu , David Woodhouse , Brian Norris , Marek Vasut , Cyrille Pitchen , Thierry Reding , Richard Genoud , Greg Kroah-Hartman , Alan Stern Cc: linux-clk@vger.kernel.org, LKML , linux-iio@vger.kernel.org, linux-mtd , linux-pwm@vger.kernel.org, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, linux-arm-kernel , Romain Izard Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5004 Lines: 119 2017-09-08 17:36 GMT+02:00 Romain Izard : > The atmel serial port driver reported the following warning on suspend: > atmel_usart f8020000.serial: ttyS1: Unable to drain transmitter > > As the ATMEL_US_TXEMPTY status bit in ATMEL_US_CSR is always cleared > when the transmitter is disabled, we need to know the transmitter's > state to return the real fifo state. And as ATMEL_US_CR is write-only, > it is necessary to save the state of the transmitter in a local > variable, and update the variable when TXEN and TXDIS is written in > ATMEL_US_CR. > > After those changes, atmel_tx_empty can return "empty" on suspend, the > warning in uart_suspend_port disappears, and suspending is 20ms shorter > for each enabled Atmel serial port. > > Signed-off-by: Romain Izard > --- > drivers/tty/serial/atmel_serial.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c > index 7551cab438ff..195c0d1b594e 100644 > --- a/drivers/tty/serial/atmel_serial.c > +++ b/drivers/tty/serial/atmel_serial.c > @@ -171,6 +171,7 @@ struct atmel_uart_port { > bool has_hw_timer; > struct timer_list uart_timer; > > + bool tx_stopped; > bool suspended; > unsigned int pending; > unsigned int pending_status; > @@ -380,6 +381,10 @@ static int atmel_config_rs485(struct uart_port *port, > */ > static u_int atmel_tx_empty(struct uart_port *port) > { > + struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); > + > + if (atmel_port->tx_stopped) > + return TIOCSER_TEMT; > return (atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXEMPTY) ? > TIOCSER_TEMT : > 0; > @@ -485,6 +490,7 @@ static void atmel_stop_tx(struct uart_port *port) > * is fully transmitted. > */ > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS); > + atmel_port->tx_stopped = true; > > /* Disable interrupts */ > atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask); > @@ -492,6 +498,7 @@ static void atmel_stop_tx(struct uart_port *port) > if ((port->rs485.flags & SER_RS485_ENABLED) && > !(port->rs485.flags & SER_RS485_RX_DURING_TX)) > atmel_start_rx(port); > + > } > > /* > @@ -521,6 +528,7 @@ static void atmel_start_tx(struct uart_port *port) > > /* re-enable the transmitter */ > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN); > + atmel_port->tx_stopped = false; > } > > /* > @@ -1866,6 +1874,7 @@ static int atmel_startup(struct uart_port *port) > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX); > /* enable xmit & rcvr */ > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN); > + atmel_port->tx_stopped = false; > > setup_timer(&atmel_port->uart_timer, > atmel_uart_timer_callback, > @@ -2122,6 +2131,7 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, > > /* disable receiver and transmitter */ > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS | ATMEL_US_RXDIS); > + atmel_port->tx_stopped = true; > > /* mode */ > if (port->rs485.flags & SER_RS485_ENABLED) { > @@ -2207,6 +2217,7 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, > atmel_uart_writel(port, ATMEL_US_BRGR, quot); > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX); > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN); > + atmel_port->tx_stopped = false; > > /* restore interrupts */ > atmel_uart_writel(port, ATMEL_US_IER, imr); > @@ -2450,6 +2461,7 @@ static void atmel_console_write(struct console *co, const char *s, u_int count) > > /* Make sure that tx path is actually able to send characters */ > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN); > + atmel_port->tx_stopped = false; > > uart_console_write(port, s, count, atmel_console_putchar); > > @@ -2528,6 +2540,7 @@ static int __init atmel_console_setup(struct console *co, char *options) > atmel_uart_writel(port, ATMEL_US_IDR, -1); > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX); > atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN); > + atmel_port->tx_stopped = false; > > if (options) > uart_parse_options(options, &baud, &parity, &bits, &flow); > -- > 2.11.0 > Unfortunately this patch was broken when I reported it from my branch to the v4.13, as it does not build because of the missing declaration of 'atmel_port' in 'atmel_console_setup'. I'll send a corrected version for v2. -- Romain Izard