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

[Ilpo Järvinen]

On Tue, 17 Jan 2023, Sergey Organov wrote:

> Ilpo Järvinen <ilpo.jarvinen at linux.intel.com> writes:
> 
> > 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.
> 
> OK, thanks, will do it this way. Probably with global rename over this
> function in a separate patch?

Yes, it is better to have it in own patch.

-- 
 i.