Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751479AbdISKSa (ORCPT ); Tue, 19 Sep 2017 06:18:30 -0400 Received: from esa3.microchip.iphmx.com ([68.232.153.233]:4856 "EHLO esa3.microchip.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751205AbdISKSZ (ORCPT ); Tue, 19 Sep 2017 06:18:25 -0400 X-IronPort-AV: E=Sophos;i="5.42,417,1500966000"; d="scan'208";a="7163947" Subject: Re: [PATCH v2 9/9] tty/serial: atmel: Prevent a warning on suspend To: Romain Izard , Alexandre Belloni , Boris Brezillon , Michael Turquette , Stephen Boyd , Ludovic Desroches , Wenyou Yang , Josh Wu , David Woodhouse , Brian Norris , Marek Vasut , Cyrille Pitchen , Thierry Reding , Richard Genoud , Greg Kroah-Hartman , Alan Stern CC: , , , , , , References: <20170915140411.31716-1-romain.izard.pro@gmail.com> <20170915140411.31716-10-romain.izard.pro@gmail.com> From: Nicolas Ferre Organization: microchip Message-ID: <380a15d6-c180-316f-a56b-011acd02df59@microchip.com> Date: Tue, 19 Sep 2017 12:19:33 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20170915140411.31716-10-romain.izard.pro@gmail.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4781 Lines: 126 On 15/09/2017 at 16:04, Romain Izard wrote: > 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 Tested-by: Nicolas Ferre on sama5d2 Xplained. Acked-by: Nicolas Ferre > --- > drivers/tty/serial/atmel_serial.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c > index 7551cab438ff..783af6648be0 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); > > @@ -2511,6 +2523,7 @@ static int __init atmel_console_setup(struct console *co, char *options) > { > int ret; > struct uart_port *port = &atmel_ports[co->index].uart; > + struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); > int baud = 115200; > int bits = 8; > int parity = 'n'; > @@ -2528,6 +2541,7 @@ 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); > -- Nicolas Ferre