lkml.org 
[lkml]   [2020]   [Jan]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] tty/serial: atmel: RS485 & ISO7816: wait for TXRDY before sending data
From
Date
Le 07/01/2020 à 12:17, Codrin.Ciubotariu@microchip.com a écrit :
> At this moment, TXEMPTY is checked before sending data on RS485 and ISO7816
> modes. However, TXEMPTY is risen when FIFO (if used) or the Transmit Shift
> Register are empty, even though TXRDY might be up and controller is able to
> receive data. Since the controller sends data only when TXEMPTY is ready,
> on RS485, when DMA is not used, the RTS pin is driven low after each byte.
> With this patch, the characters will be transmitted when TXRDY is up and
> so, RTS pin will remain high between bytes.
> The performance improvement on RS485 is about 8% with a baudrate of 300.
>
> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
seems ok to me
Acked-by: Richard Genoud <richard.genoud@gmail.com>

NB: MS exchange has added some =3D and =20 here and there, but git am
doesn't seems to be bothered by them.
> ---
> drivers/tty/serial/atmel_serial.c | 26 +++++++++++++++++++-------
> 1 file changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index a8dc8af83f39..19c8fb9faa36 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -313,7 +313,11 @@ static int atmel_config_rs485(struct uart_port *port,
>
> if (rs485conf->flags & SER_RS485_ENABLED) {
> dev_dbg(port->dev, "Setting UART to RS485\n");
> - atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
> + if (port->rs485.flags & SER_RS485_RX_DURING_TX)
> + atmel_port->tx_done_mask = ATMEL_US_TXRDY;
> + else
> + atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
> +
> atmel_uart_writel(port, ATMEL_US_TTGR,
> rs485conf->delay_rts_after_send);
> mode |= ATMEL_US_USMODE_RS485;
> @@ -831,7 +835,7 @@ static void atmel_tx_chars(struct uart_port *port)
> struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
>
> if (port->x_char &&
> - (atmel_uart_readl(port, ATMEL_US_CSR) & atmel_port->tx_done_mask)) {
> + (atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY)) {
> atmel_uart_write_char(port, port->x_char);
> port->icount.tx++;
> port->x_char = 0;
> @@ -839,8 +843,7 @@ static void atmel_tx_chars(struct uart_port *port)
> if (uart_circ_empty(xmit) || uart_tx_stopped(port))
> return;
>
> - while (atmel_uart_readl(port, ATMEL_US_CSR) &
> - atmel_port->tx_done_mask) {
> + while (atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY) {
> atmel_uart_write_char(port, xmit->buf[xmit->tail]);
> xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
> port->icount.tx++;
> @@ -851,10 +854,20 @@ static void atmel_tx_chars(struct uart_port *port)
> if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
> uart_write_wakeup(port);
>
> - if (!uart_circ_empty(xmit))
> + if (!uart_circ_empty(xmit)) {
> + /* we still have characters to transmit, so we should continue
> + * transmitting them when TX is ready, regardless of
> + * mode or duplexity
> + */
> + atmel_port->tx_done_mask |= ATMEL_US_TXRDY;
> +
> /* Enable interrupts */
> atmel_uart_writel(port, ATMEL_US_IER,
> atmel_port->tx_done_mask);
> + } else {
> + if (atmel_uart_is_half_duplex(port))
> + atmel_port->tx_done_mask &= ~ATMEL_US_TXRDY;
> + }
> }
>
> static void atmel_complete_tx_dma(void *arg)
> @@ -2525,8 +2538,7 @@ static int atmel_init_port(struct atmel_uart_port *atmel_port,
> * Use TXEMPTY for interrupt when rs485 or ISO7816 else TXRDY or
> * ENDTX|TXBUFE
> */
> - if (port->rs485.flags & SER_RS485_ENABLED ||
> - port->iso7816.flags & SER_ISO7816_ENABLED)
> + if (atmel_uart_is_half_duplex(port))
> atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
> else if (atmel_use_pdc_tx(port)) {
> port->fifosize = PDC_BUFFER_SIZE;
>

\
 
 \ /
  Last update: 2020-01-08 14:45    [W:0.069 / U:9.104 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site