linux-kernel - [PATCH v3] serial: uartps: Add TACTIVE bit in cdns_uart_tx

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Date:   Fri, 31 Jan 2020 16:34:45 +0530
From:   Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
To:     linux-serial@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, jslaby@...e.com,
        michal.simek@...inx.com, linux-kernel@...r.kernel.org,
        Raviteja Narayanam <raviteja.narayanam@...inx.com>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
Subject: [PATCH v3] serial: uartps: Add TACTIVE bit in cdns_uart_tx_empty function

From: Raviteja Narayanam <raviteja.narayanam@...inx.com>

Make sure that all the bytes are transmitted out of Uart by monitoring
TACTIVE bit as well.
Before setting up baud rate in set termios function, do not wait for
Tx empty as it is taken care by the tty layer if user specified.

Signed-off-by: Raviteja Narayanam <raviteja.narayanam@...inx.com>
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
---
v3:
removed the wait from the set_termios and added the TACTIVE to cdns_uart_tx_empty
As suggested by Johan.

 drivers/tty/serial/xilinx_uartps.c | 22 +++++-----------------
 1 file changed, 5 insertions(+), 17 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index ed2f325..ebd0a74 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -32,7 +32,6 @@
 #define CDNS_UART_NAME		"xuartps"
 #define CDNS_UART_FIFO_SIZE	64	/* FIFO size */
 #define CDNS_UART_REGISTER_SPACE	0x1000
-#define TX_TIMEOUT		500000
 
 /* Rx Trigger level */
 static int rx_trigger_level = 56;
@@ -656,8 +655,9 @@ static unsigned int cdns_uart_tx_empty(struct uart_port *port)
 {
 	unsigned int status;
 
-	status = readl(port->membase + CDNS_UART_SR) &
-				CDNS_UART_SR_TXEMPTY;
+	status = ((readl(port->membase + CDNS_UART_SR) &
+				(CDNS_UART_SR_TXEMPTY |
+				CDNS_UART_SR_TACTIVE)) == CDNS_UART_SR_TXEMPTY);
 	return status ? TIOCSER_TEMT : 0;
 }
 
@@ -700,20 +700,8 @@ static void cdns_uart_set_termios(struct uart_port *port,
 	u32 cval = 0;
 	unsigned int baud, minbaud, maxbaud;
 	unsigned long flags;
-	unsigned int ctrl_reg, mode_reg, val;
-	int err;
-
-	/* Wait for the transmit FIFO to empty before making changes */
-	if (!(readl(port->membase + CDNS_UART_CR) &
-				CDNS_UART_CR_TX_DIS)) {
-		err = readl_poll_timeout(port->membase + CDNS_UART_SR,
-					 val, (val & CDNS_UART_SR_TXEMPTY),
-					 1000, TX_TIMEOUT);
-		if (err) {
-			dev_err(port->dev, "timed out waiting for tx empty");
-			return;
-		}
-	}
+	unsigned int ctrl_reg, mode_reg;
+
 	spin_lock_irqsave(&port->lock, flags);
 
 	/* Disable the TX and RX to set baud rate */
-- 
2.7.4