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serial: mxc: Speed-up character transmission

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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>
Reviewed-by: Fabio Estevam <festevam@denx.de>
Tested-by: Fabio Estevam <festevam@denx.de>
This commit is contained in:
Loic Poulain 2023-01-12 18:19:51 +01:00 committed by Stefano Babic
parent 7150f56a85
commit ad725073d1
1 changed files with 4 additions and 4 deletions
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8
drivers/serial/serial_mxc.c
View file

@ -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);