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tty/serial: atmel: Prevent a warning on suspend 

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@gmail.com>
Tested-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Romain Izard 2017-09-28 11:46:27 +02:00 committed by Greg Kroah-Hartman
parent fa2abb0363
commit ea04f82a0c
1 changed files with 13 additions and 0 deletions
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13
drivers/tty/serial/atmel_serial.c
View File

@ -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;
}
/*
@ -1843,6 +1850,7 @@ 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,
@ -2099,6 +2107,7 @@ 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) {
@ -2184,6 +2193,7 @@ 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);
@ -2427,6 +2437,7 @@ 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);
@ -2488,6 +2499,7 @@ 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';
@ -2505,6 +2517,7 @@ 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);