[PATCH v1 10/10] tty/serial: atmel: Prevent a warning on suspend
From: Romain Izard <hidden>
Date: 2017-09-08 15:37:28
Also in:
linux-arm-kernel, linux-clk, linux-iio, linux-pwm, lkml
Subsystem:
microchip at91 serial driver, the rest, tty layer and serial drivers · Maintainers:
Richard Genoud, Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
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 <redacted> --- 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