2022-05-02 05:59:09

by Shubhrajyoti Datta

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 <[email protected]>
---
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

2022-05-08 09:25:42

by Greg Kroah-Hartman

Subject: Re: [PATCH 7/7] serial: uartps: Prevent writes when the controller is disabled

On Fri, Apr 29, 2022 at 01:44:22PM +0530, Shubhrajyoti Datta wrote:
> Prevent writing to the fifo if the controller is disabled.
>
> Signed-off-by: Shubhrajyoti Datta <[email protected]>
> ---
> 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();

You are spinning for forever? With no timeout possible?

That's not ok :(


> + }
> while (readl(port->membase + CDNS_UART_SR) & CDNS_UART_SR_TXFULL)
> cpu_relax();

Ick, same here, you better hope your hardware works...

thanks,

greg k-h