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[109.3.187.146]) by smtp.gmail.com with ESMTPSA id r6sm9699900wrg.40.2017.09.27.01.36.19 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Sep 2017 01:36:20 -0700 (PDT) From: Romain Izard To: Boris Brezillon , Michael Turquette , Stephen Boyd , Lee Jones , Wenyou Yang , Josh Wu , Richard Weinberger , David Woodhouse , Brian Norris , Marek Vasut , Cyrille Pitchen , Thierry Reding , Richard Genoud , Greg Kroah-Hartman , Jiri Slaby , Alan Stern , Ludovic Desroches , Nicolas Ferre , Alexandre Belloni Cc: linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-pwm@vger.kernel.org, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, Romain Izard Subject: [PATCH v3 8/8] tty/serial: atmel: Prevent a warning on suspend Date: Wed, 27 Sep 2017 10:35:55 +0200 Message-Id: <20170927083555.16580-9-romain.izard.pro@gmail.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170927083555.16580-1-romain.izard.pro@gmail.com> References: <20170927083555.16580-1-romain.izard.pro@gmail.com> Sender: linux-pwm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org 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 Acked-by: Nicolas Ferre Acked-by: Richard Genoud --- 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..ce45b4ada0bf 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); @@ -521,6 +527,7 @@ 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 +1873,7 @@ 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 +2130,7 @@ 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 +2216,7 @@ 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 +2460,7 @@ 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 +2522,7 @@ 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 +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);