[PATCH 7/8] serial: imx: use readl() to optimize FIFO reading loop

[Ilpo Järvinen]

On Fri, 13 Jan 2023, Sergey Organov wrote:

> Use readl() instead of heavier imx_uart_readl() in the Rx ISR, as we know
> we read registers that must not be cached.
> 
> Signed-off-by: Sergey Organov <sorganov at gmail.com>
> ---
>  drivers/tty/serial/imx.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index be00362b8b67..f4236e8995fa 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -890,14 +890,15 @@ static irqreturn_t __imx_uart_rxint(int irq, void *dev_id)
>  	struct imx_port *sport = dev_id;
>  	unsigned int rx, flg;
>  	struct tty_port *port = &sport->port.state->port;
> +	typeof(sport->port.membase) membase = sport->port.membase;
>  	u32 usr2;
>  
>  	/* If we received something, check for 0xff flood */
> -	usr2 = imx_uart_readl(sport, USR2);
> +	usr2 = readl(membase + USR2);
>  	if (usr2 & USR2_RDR)
>  		imx_uart_check_flood(sport, usr2);
>  
> -	while ((rx = imx_uart_readl(sport, URXD0)) & URXD_CHARRDY) {
> +	while ((rx = readl(membase + URXD0)) & URXD_CHARRDY) {
>  		flg = TTY_NORMAL;
>  		sport->port.icount.rx++;

I'd just make a uport local variable and use uport->membase + xx. There 
are plenty of sport->port constructs to replace with uport in that 
function anyway.

-- 
 i.