From ad725073d1666d94a96fbf9cba03777c3d58de24 Mon Sep 17 00:00:00 2001
From: Loic Poulain <loic.poulain@linaro.org>
Date: Thu, 12 Jan 2023 18:19:51 +0100
Subject: [PATCH] serial: mxc: Speed-up character transmission
MIME-Version: 1.0
Content-Type: text/plain; charset=utf8
Content-Transfer-Encoding: 8bit
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 WaÃmann <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>
---
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 e4ffa9c3f6..cc85a50272 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);
--
2.39.5