serial: tegra: protect IER against LCR.DLAB

The IER and DLH registers occupy the same address space, selected by
the LCR.DLAB bit. Hence, add port lock to protect IER when LCR.DLAB bit
is set.

Signed-off-by: Ahung Cheng <ahcheng@nvidia.com>
Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/1565609303-27000-5-git-send-email-kyarlagadda@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index 83cc8dc..82a8d51 100644 (file)
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -294,6 +294,7 @@ static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)
        unsigned long rate;
        unsigned int divisor;
        unsigned long lcr;
+       unsigned long flags;
        int ret;
 
        if (tup->current_baud == baud)
@@ -313,6 +314,7 @@ static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)
                divisor = DIV_ROUND_CLOSEST(rate, baud * 16);
        }
 
+       spin_lock_irqsave(&tup->uport.lock, flags);
        lcr = tup->lcr_shadow;
        lcr |= UART_LCR_DLAB;
        tegra_uart_write(tup, lcr, UART_LCR);
@@ -325,6 +327,7 @@ static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)
 
        /* Dummy read to ensure the write is posted */
        tegra_uart_read(tup, UART_SCR);
+       spin_unlock_irqrestore(&tup->uport.lock, flags);
 
        tup->current_baud = baud;