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@linaro.org Tested-by: Lothar Waßmann LW@KARO-electronics.de Acked-by: Pali Rohár pali@kernel.org --- v2: fixing transfert abort & char corruption commit v3: Reordering commits for good bisectability v4: no code change
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 9e5b987994..cac1922354 100644 --- a/drivers/serial/serial_mxc.c +++ b/drivers/serial/serial_mxc.c @@ -240,11 +240,11 @@ 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 */ @@ -335,7 +335,7 @@ 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);