linux-kernel - [PATCH 7/7] serial: uartps: Prevent writes when the controller is disabled

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Date:   Fri, 29 Apr 2022 13:44:22 +0530
From:   Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
To:     <linux-serial@...r.kernel.org>
CC:     <michal.simek@...inx.com>, <jirislaby@...nel.org>,
        <gregkh@...uxfoundation.org>, <git@...inx.com>,
        <linux-kernel@...r.kernel.org>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
Subject: [PATCH 7/7] serial: uartps: Prevent writes when the controller is disabled

Prevent writing to the fifo if the controller is disabled.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
---
 drivers/tty/serial/xilinx_uartps.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 81ba69c57716..f629c4ca940f 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1150,6 +1150,13 @@ static struct uart_driver cdns_uart_uart_driver;
  */
 static void cdns_uart_console_putchar(struct uart_port *port, unsigned char ch)
 {
+	unsigned int ctrl_reg;
+
+	ctrl_reg = readl(port->membase + CDNS_UART_CR);
+	while (ctrl_reg & CDNS_UART_CR_TX_DIS) {
+		ctrl_reg = readl(port->membase + CDNS_UART_CR);
+		cpu_relax();
+	}
 	while (readl(port->membase + CDNS_UART_SR) & CDNS_UART_SR_TXFULL)
 		cpu_relax();
 	writel(ch, port->membase + CDNS_UART_FIFO);
-- 
2.25.1