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    Subject[PATCH 5.13 758/800] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available
    Date
    From: Pali Rohár <pali@kernel.org>

    [ Upstream commit ecd6b010d81f97b06b2f64d2d4f50ebf5acddaa9 ]

    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@kernel.org>
    Fixes: 68a0db1d7da2 ("serial: mvebu-uart: add function to change baudrate")
    Link: https://lore.kernel.org/r/20210624224909.6350-3-pali@kernel.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 908a4ac6b5a7..9638ae6aae79 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:
    --
    2.30.2


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