[PATCH 6/8] serial: imx: stop using USR2 in FIFO reading loop

[Ilpo Järvinen]

On Fri, 13 Jan 2023, Sergey Organov wrote:

> The chip provides all the needed bits in the URXD0 register that we read
> anyway for data, so get rid of reading USR2 and use only URXD0 bits
> instead.
> 
> Signed-off-by: Sergey Organov <sorganov at gmail.com>
> ---
>  drivers/tty/serial/imx.c | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index c44a7293c013..be00362b8b67 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -892,27 +892,21 @@ static irqreturn_t __imx_uart_rxint(int irq, void *dev_id)
>  	struct tty_port *port = &sport->port.state->port;
>  	u32 usr2;
>  
> -	usr2 = imx_uart_readl(sport, USR2);
> -
>  	/* If we received something, check for 0xff flood */
> +	usr2 = imx_uart_readl(sport, USR2);

Please just place the read into the correct place in 2/8 rather than 
moving it needlessly here again.

-- 
 i.


>  	if (usr2 & USR2_RDR)
>  		imx_uart_check_flood(sport, usr2);
>  
> -	for ( ; usr2 & USR2_RDR; usr2 = imx_uart_readl(sport, USR2)) {
> +	while ((rx = imx_uart_readl(sport, URXD0)) & URXD_CHARRDY) {
>  		flg = TTY_NORMAL;
>  		sport->port.icount.rx++;
>  
> -		rx = imx_uart_readl(sport, URXD0);
> -
> -		if (usr2 & USR2_BRCD) {
> -			imx_uart_writel(sport, USR2_BRCD, USR2);
> -			if (uart_handle_break(&sport->port))
> -				continue;
> -		}
> -
>  		if (unlikely(rx & URXD_ERR)) {
> -			if (rx & URXD_BRK)
> +			if (rx & URXD_BRK) {
>  				sport->port.icount.brk++;
> +				if (uart_handle_break(&sport->port))
> +					continue;
> +			}
>  			else if (rx & URXD_PRERR)
>  				sport->port.icount.parity++;
>  			else if (rx & URXD_FRMERR)
>