[PATCH v2 9/9] tty/serial: atmel: Prevent a warning on suspend

[Nicolas Ferre]

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 <romain.izard.pro at gmail.com>

Tested-by: Nicolas Ferre <nicolas.ferre at microchip.com>
on sama5d2 Xplained.

Acked-by: Nicolas Ferre <nicolas.ferre at microchip.com>

> ---
>  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