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

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Date:   Sat, 01 Feb 2020 12:29:15 +0100
From:   Maarten Brock <m.brock@...mierlo.com>
To:     Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
Cc:     linux-serial@...r.kernel.org, gregkh@...uxfoundation.org,
        jslaby@...e.com, michal.simek@...inx.com,
        linux-kernel@...r.kernel.org,
        Raviteja Narayanam <raviteja.narayanam@...inx.com>,
        linux-serial-owner@...r.kernel.org
Subject: Re: [PATCH v3] serial: uartps: Add TACTIVE bit in cdns_uart_tx_empty
 function

On 2020-01-31 12:04, Shubhrajyoti Datta wrote:
>  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
> @@ -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;
>  }

These lines look pretty incomprehensible.
How about rewriting it like this?

     status = readl(port->membase + CDNS_UART_SR) &
              (CDNS_UART_SR_TXEMPTY | CDNS_UART_SR_TACTIVE);
     return (status == CDNS_UART_SR_TXEMPTY) ? TIOCSER_TEMT : 0;

Maarten