[PATCH v3 2/2] serial: mxc: Speed-up character transmission

[Loic Poulain]

On Wed, 11 Jan 2023 at 00:55, Pali Rohár <pali at kernel.org> wrote:
>
> On Tuesday 10 January 2023 20:24:07 Loic Poulain wrote:
> > Instead of waiting for empty FIFO condition before writing a
> > character, wait for non-full FIFO condition.
> >
> > This helps in saving several tens of milliseconds during boot
> > (depending verbosity).
> >
> > Signed-off-by: Loic Poulain <loic.poulain at linaro.org>
> > Tested-by: Lothar Waßmann <LW at KARO-electronics.de>
> > ---
> >  v2: fixing transfert abort & char corruption commit
> >  v3: Reordering commits for good bisectability
> >
> >  drivers/serial/serial_mxc.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/serial/serial_mxc.c b/drivers/serial/serial_mxc.c
> > index 3c89781f2c..9899155c00 100644
> > --- a/drivers/serial/serial_mxc.c
> > +++ b/drivers/serial/serial_mxc.c
> > @@ -238,11 +238,11 @@ static void mxc_serial_putc(const char c)
> >       if (c == '\n')
> >               serial_putc('\r');
> >
> > -     writel(c, &mxc_base->txd);
> > -
> >       /* wait for transmitter to be ready */
> > -     while (!(readl(&mxc_base->ts) & UTS_TXEMPTY))
> > +     while (readl(&mxc_base->ts) & UTS_TXFULL)
> >               schedule();
> > +
> > +     writel(c, &mxc_base->txd);
> >  }
> >
> >  /* Test whether a character is in the RX buffer */
> > @@ -333,7 +333,7 @@ static int mxc_serial_putc(struct udevice *dev, const char ch)
> >       struct mxc_serial_plat *plat = dev_get_plat(dev);
> >       struct mxc_uart *const uart = plat->reg;
> >
> > -     if (!(readl(&uart->ts) & UTS_TXEMPTY))
> > +     if (readl(&uart->ts) & UTS_TXFULL)
> >               return -EAGAIN;
> >
> >       writel(ch, &uart->txd);
> > --
> > 2.34.1
> >
>
> Hello!
>
> In this driver there are two mxc_serial_putc() and two mxc_serial_getc()
> function. One for DM and one for non-DM version. It would be really nice
> to fix also second set of functions.

This commit changes both DM/non-DM putc() functions.

Regards,
Loic