linux-kernel - [PATCH 02/10] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available

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Date:   Fri, 25 Jun 2021 00:49:01 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Vladimir Vid <vladimir.vid@...tura.hr>,
        Marek Behún <kabel@...nel.org>,
        linux-clk@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 02/10] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available

Testing mvuart->clk for non-error is not enough as mvuart->clk may contain
valid clk pointer but when clk_prepare_enable(mvuart->clk) failed then
port->uartclk is zero.

When mvuart->clk is not available then port->uartclk is zero too.

Parent clock rate port->uartclk is needed to calculate UART clock divisor
and without it is not possible to change baudrate.

So fix test condition when it is possible to change baudrate.

Signed-off-by: Pali Rohár <pali@...nel.org>
Fixes: 68a0db1d7da2 ("serial: mvebu-uart: add function to change baudrate")
---
 drivers/tty/serial/mvebu-uart.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c
index f81bfdaa608c..dc0c26824ddb 100644
--- a/drivers/tty/serial/mvebu-uart.c
+++ b/drivers/tty/serial/mvebu-uart.c
@@ -445,12 +445,11 @@ static void mvebu_uart_shutdown(struct uart_port *port)
 
 static int mvebu_uart_baud_rate_set(struct uart_port *port, unsigned int baud)
 {
-	struct mvebu_uart *mvuart = to_mvuart(port);
 	unsigned int d_divisor, m_divisor;
 	u32 brdv, osamp;
 
-	if (IS_ERR(mvuart->clk))
-		return -PTR_ERR(mvuart->clk);
+	if (!port->uartclk)
+		return -EOPNOTSUPP;
 
 	/*
 	 * The baudrate is derived from the UART clock thanks to two divisors:
-- 
2.20.1