From: <Codrin.Ciubotariu@microchip.com> To: <linux-serial@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org> Cc: <richard.genoud@gmail.com>, <gregkh@linuxfoundation.org>, <jslaby@suse.com>, <Nicolas.Ferre@microchip.com>, <alexandre.belloni@bootlin.com>, <Ludovic.Desroches@microchip.com>, <Codrin.Ciubotariu@microchip.com> Subject: [PATCH] tty/serial: atmel: RS485 & ISO7816: wait for TXRDY before sending data Date: Tue, 7 Jan 2020 11:17:47 +0000 [thread overview] Message-ID: <20200107111656.26308-1-codrin.ciubotariu@microchip.com> (raw) 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> --- 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; -- 2.20.1
WARNING: multiple messages have this Message-ID (diff)
From: <Codrin.Ciubotariu@microchip.com> To: <linux-serial@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org> Cc: alexandre.belloni@bootlin.com, richard.genoud@gmail.com, gregkh@linuxfoundation.org, Ludovic.Desroches@microchip.com, jslaby@suse.com, Codrin.Ciubotariu@microchip.com Subject: [PATCH] tty/serial: atmel: RS485 & ISO7816: wait for TXRDY before sending data Date: Tue, 7 Jan 2020 11:17:47 +0000 [thread overview] Message-ID: <20200107111656.26308-1-codrin.ciubotariu@microchip.com> (raw) 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> --- 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; -- 2.20.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2020-01-07 11:17 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-07 11:17 Codrin.Ciubotariu [this message] 2020-01-07 11:17 ` [PATCH] tty/serial: atmel: RS485 & ISO7816: wait for TXRDY before sending data Codrin.Ciubotariu 2020-01-08 13:45 ` Richard Genoud 2020-01-08 13:45 ` Richard Genoud 2020-01-08 16:03 ` Codrin.Ciubotariu 2020-01-08 16:03 ` Codrin.Ciubotariu 2020-01-09 7:33 ` Uwe Kleine-König 2020-01-09 7:33 ` Uwe Kleine-König 2020-01-09 8:52 ` Richard Genoud 2020-01-09 8:52 ` Richard Genoud
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