From: Yu Tu <yu.tu@amlogic.com>
To: <linux-serial@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-amlogic@lists.infradead.org>,
<linux-kernel@vger.kernel.org>,
Neil Armstrong <narmstrong@baylibre.com>,
Kevin Hilman <khilman@baylibre.com>,
Jerome Brunet <jbrunet@baylibre.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jirislaby@kernel.org>,
Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
Yu Tu <yu.tu@amlogic.com>
Subject: [PATCH 1/3] tty: serial: meson: Use DIV_ROUND_CLOSEST to calculate baud rates
Date: Thu, 7 Apr 2022 16:13:53 +0800 [thread overview]
Message-ID: <20220407081355.13602-2-yu.tu@amlogic.com> (raw)
In-Reply-To: <20220407081355.13602-1-yu.tu@amlogic.com>
Due to chip process differences, chip designers recommend using baud
rates as close to and larger as possible in order to reduce clock
errors.
Signed-off-by: Yu Tu <yu.tu@amlogic.com>
---
drivers/tty/serial/meson_uart.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 2bf1c57e0981..8e59624935af 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -299,10 +299,10 @@ static void meson_uart_change_speed(struct uart_port *port, unsigned long baud)
cpu_relax();
if (port->uartclk == 24000000) {
- val = ((port->uartclk / 3) / baud) - 1;
+ val = DIV_ROUND_CLOSEST(port->uartclk / 3, baud) - 1;
val |= AML_UART_BAUD_XTAL;
} else {
- val = ((port->uartclk * 10 / (baud * 4) + 5) / 10) - 1;
+ val = DIV_ROUND_CLOSEST(port->uartclk / 4, baud) - 1;
}
val |= AML_UART_BAUD_USE;
writel(val, port->membase + AML_UART_REG5);
--
2.33.1
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next prev parent reply other threads:[~2022-04-07 8:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-07 8:13 [PATCH 0/3] Use DIV_ROUND_CLOSEST to calculate baud rate, Yu Tu
2022-04-07 8:13 ` Yu Tu [this message]
2022-04-07 13:56 ` [PATCH 1/3] tty: serial: meson: Use DIV_ROUND_CLOSEST to calculate baud rates Neil Armstrong
2022-04-07 8:13 ` [PATCH 2/3] tty: serial: meson: Added 12Mhz as the clock source for calculating baud rate Yu Tu
2022-04-07 14:03 ` Neil Armstrong
2022-04-15 13:35 ` Yu Tu
2022-04-07 8:13 ` [PATCH 3/3] tty: serial: meson: Added S4 SOC compatibility Yu Tu
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