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From: "Pali Rohár" <pali@kernel.org>
To: Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>, Rob Herring <robh+dt@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Andrew Lunn" <andrew@lunn.ch>,
	"Gregory Clement" <gregory.clement@bootlin.com>,
	"Sebastian Hesselbarth" <sebastian.hesselbarth@gmail.com>,
	"Vladimir Vid" <vladimir.vid@sartura.hr>,
	"Marek Behún" <kabel@kernel.org>,
	"Geert Uytterhoeven" <geert@linux-m68k.org>,
	linux-clk@vger.kernel.org, linux-serial@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 03/11] serial: mvebu-uart: correctly calculate minimal possible baudrate
Date: Fri, 25 Jun 2021 16:36:09 +0200	[thread overview]
Message-ID: <20210625143617.12826-4-pali@kernel.org> (raw)
In-Reply-To: <20210625143617.12826-1-pali@kernel.org>

For default (x16) scheme which is currently used by mvebu-uart.c driver,
maximal divisor of UART base clock is 1023*16. Therefore there is limit for
minimal supported baudrate. This change calculate it correctly and prevents
setting invalid divisor 0 into hardware registers.

Signed-off-by: Pali Rohár <pali@kernel.org>
Fixes: 68a0db1d7da2 ("serial: mvebu-uart: add function to change baudrate")
---
 drivers/tty/serial/mvebu-uart.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c
index dc0c26824ddb..f8b0016db847 100644
--- a/drivers/tty/serial/mvebu-uart.c
+++ b/drivers/tty/serial/mvebu-uart.c
@@ -481,7 +481,7 @@ static void mvebu_uart_set_termios(struct uart_port *port,
 				   struct ktermios *old)
 {
 	unsigned long flags;
-	unsigned int baud;
+	unsigned int baud, min_baud, max_baud;
 
 	spin_lock_irqsave(&port->lock, flags);
 
@@ -500,16 +500,21 @@ static void mvebu_uart_set_termios(struct uart_port *port,
 		port->ignore_status_mask |= STAT_RX_RDY(port) | STAT_BRK_ERR;
 
 	/*
+	 * Maximal divisor is 1023 * 16 when using default (x16) scheme.
 	 * Maximum achievable frequency with simple baudrate divisor is 230400.
 	 * Since the error per bit frame would be of more than 15%, achieving
 	 * higher frequencies would require to implement the fractional divisor
 	 * feature.
 	 */
-	baud = uart_get_baud_rate(port, termios, old, 0, 230400);
+	min_baud = DIV_ROUND_UP(port->uartclk, 1023 * 16);
+	max_baud = 230400;
+
+	baud = uart_get_baud_rate(port, termios, old, min_baud, max_baud);
 	if (mvebu_uart_baud_rate_set(port, baud)) {
 		/* No clock available, baudrate cannot be changed */
 		if (old)
-			baud = uart_get_baud_rate(port, old, NULL, 0, 230400);
+			baud = uart_get_baud_rate(port, old, NULL,
+						  min_baud, max_baud);
 	} else {
 		tty_termios_encode_baud_rate(termios, baud, baud);
 		uart_update_timeout(port, termios->c_cflag, baud);
-- 
2.20.1


  parent reply	other threads:[~2021-06-25 14:37 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24 22:48 [PATCH 00/10] serial: mvebu-uart: Fixes and new support for higher baudrates Pali Rohár
2021-06-24 22:49 ` [PATCH 01/10] serial: mvebu-uart: fix calculation of clock divisor Pali Rohár
2021-06-24 22:49 ` [PATCH 02/10] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available Pali Rohár
2021-06-24 22:49 ` [PATCH 03/10] serial: mvebu-uart: correctly calculate minimal possible baudrate Pali Rohár
2021-06-24 22:49 ` [PATCH 04/10] dt-bindings: mvebu-uart: fix documentation Pali Rohár
2021-06-24 22:49 ` [PATCH 05/10] arm64: dts: marvell: armada-37xx: Fix reg for standard variant of UART Pali Rohár
2021-06-24 22:49 ` [PATCH 06/10] serial: mvebu-uart: remove unused member nb from struct mvebu_uart Pali Rohár
2021-06-24 22:49 ` [PATCH 07/10] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-06-24 22:49 ` [PATCH 08/10] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-06-24 22:49 ` [PATCH 09/10] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-06-24 22:49 ` [PATCH 10/10] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-06-25 14:36 ` [PATCH v2 00/11] serial: mvebu-uart: Fixes and new support for higher baudrates Pali Rohár
2021-06-25 14:36   ` [PATCH v2 01/11] serial: mvebu-uart: fix calculation of clock divisor Pali Rohár
2021-06-25 14:36   ` [PATCH v2 02/11] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available Pali Rohár
2021-06-25 14:36   ` Pali Rohár [this message]
2021-06-25 14:36   ` [PATCH v2 04/11] dt-bindings: mvebu-uart: fix documentation Pali Rohár
2021-06-25 14:36   ` [PATCH v2 05/11] arm64: dts: marvell: armada-37xx: Fix reg for standard variant of UART Pali Rohár
2021-06-25 14:36   ` [PATCH v2 06/11] serial: mvebu-uart: remove unused member nb from struct mvebu_uart Pali Rohár
2021-06-25 14:36   ` [PATCH v2 07/11] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-06-25 15:22     ` Geert Uytterhoeven
2021-06-25 15:38       ` Pali Rohár
2021-06-25 15:50         ` Willy Tarreau
2021-06-25 17:39           ` Geert Uytterhoeven
2021-06-25 17:44             ` Pali Rohár
2021-06-25 18:11               ` Geert Uytterhoeven
2021-07-19 12:45         ` Andy Shevchenko
2021-06-25 14:36   ` [PATCH v2 08/11] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-06-25 14:36   ` [PATCH v2 09/11] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-06-25 14:36   ` [PATCH v2 10/11] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-06-25 14:36   ` [PATCH v2 11/11] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-07-17 12:38 ` [PATCH v3 0/5] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-07-17 12:38   ` [PATCH v3 1/5] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-07-19 12:47     ` Andy Shevchenko
2021-07-22 21:57       ` Pali Rohár
2021-07-24 11:38         ` David Laight
2021-07-17 12:38   ` [PATCH v3 2/5] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-07-17 17:26     ` Andrew Lunn
2021-07-17 18:05       ` Pali Rohár
2021-07-24  9:48         ` Pali Rohár
2021-07-24 16:33           ` Andrew Lunn
2021-07-25 12:14             ` Pali Rohár
2021-07-17 12:38   ` [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-07-17 17:30     ` [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Andrew Lunn
2021-08-02 14:45       ` Pali Rohár
2021-07-17 12:38   ` [PATCH v3 4/5] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-07-17 12:38   ` [PATCH v3 5/5] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-08-02 14:45 ` [PATCH v4 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-08-02 14:45   ` [PATCH v4 1/6] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-08-02 14:45   ` [PATCH v4 2/6] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-08-02 14:45   ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-08-06  0:30     ` Stephen Boyd
2021-08-06  8:28       ` Pali Rohár
2021-08-12 19:33         ` Stephen Boyd
2021-08-12 20:08           ` Pali Rohár
2021-08-02 14:45   ` [PATCH v4 4/6] dt-bindings: mvebu-uart: update information about UART clock Pali Rohár
2021-08-02 14:45   ` [PATCH v4 5/6] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-08-02 14:45   ` [PATCH v4 6/6] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-08-09 14:53 ` [PATCH v5 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-08-09 14:53   ` [PATCH v5 1/6] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-08-09 14:53   ` [PATCH v5 2/6] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-08-09 14:53   ` [PATCH v5 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-08-09 14:53   ` [PATCH v5 4/6] dt-bindings: mvebu-uart: update information about UART clock Pali Rohár
2021-08-09 14:53   ` [PATCH v5 5/6] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-08-09 14:53   ` [PATCH v5 6/6] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-08-20 17:22   ` [PATCH v5 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-08-31  8:35     ` Pali Rohár
2021-09-21  7:41       ` Greg Kroah-Hartman

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