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

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Date:   Fri, 31 Jan 2020 15:18:36 +0100
From:   Johan Hovold <johan@...nel.org>
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>
Subject: Re: [PATCH v3] serial: uartps: Add TACTIVE bit in cdns_uart_tx_empty
 function

On Fri, Jan 31, 2020 at 04:34:45PM +0530, Shubhrajyoti Datta wrote:
> 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.

Since this is two logical changes I suggest you split it in two patches;
the first removing the wait from set_termios, and the second adding the
TCACTIVE check.

> 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;

Please rewrite this to avoid some of the line breaks (e.g. split readl()
from the test).

Johan