serial: altera_uart: fix locking in polling mode

[ Upstream commit 1307c5d33cce8a41dd77c2571e4df65a5b627feb ]

Since altera_uart_interrupt() may also be called from
a poll timer in "serving_softirq" context, use
spin_[lock_irqsave|unlock_irqrestore] variants, which
are appropriate for both softirq and hardware interrupt
contexts.

Fixes: 2f8b9c15cd88 ("altera_uart: Add support for polling mode (IRQ-less)")
Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
Link: https://lore.kernel.org/r/20221122200426.888349-1-gsomlo@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/tty/serial/altera_uart.c b/drivers/tty/serial/altera_uart.c
index 6e08fa1..91799c4 100644 (file)
--- a/drivers/tty/serial/altera_uart.c
+++ b/drivers/tty/serial/altera_uart.c
@@ -278,16 +278,17 @@ static irqreturn_t altera_uart_interrupt(int irq, void *data)
 {
        struct uart_port *port = data;
        struct altera_uart *pp = container_of(port, struct altera_uart, port);
+       unsigned long flags;
        unsigned int isr;
 
        isr = altera_uart_readl(port, ALTERA_UART_STATUS_REG) & pp->imr;
 
-       spin_lock(&port->lock);
+       spin_lock_irqsave(&port->lock, flags);
        if (isr & ALTERA_UART_STATUS_RRDY_MSK)
                altera_uart_rx_chars(port);
        if (isr & ALTERA_UART_STATUS_TRDY_MSK)
                altera_uart_tx_chars(port);
-       spin_unlock(&port->lock);
+       spin_unlock_irqrestore(&port->lock, flags);
 
        return IRQ_RETVAL(isr);
 }