Commit 31fae7c8 authored by Vignesh Raghavendra's avatar Vignesh Raghavendra Committed by Greg Kroah-Hartman
Browse files

serial: 8250: 8250_omap: Fix possible interrupt storm 



It is possible that RX TIMEOUT is signalled after RX FIFO has been
drained, in which case a dummy read of RX FIFO is required to clear RX
TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
leading to an interrupt storm

Cc: stable@vger.kernel.org
Reported-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarVignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20210511151955.28071-1-vigneshr@ti.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1f06f571

drivers/tty/serial/8250/8250_omap.c

+12 −0
Original line number Diff line number Diff line
@@ -104,6 +104,9 @@ 
#define UART_OMAP_EFR2			0x23

#define UART_OMAP_EFR2_TIMEOUT_BEHAVE	BIT(6)



/* RX FIFO occupancy indicator */

#define UART_OMAP_RX_LVL		0x64



struct omap8250_priv {

	int line;

	u8 habit;
@@ -625,6 +628,15 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id) 
	serial8250_rpm_get(up);

	iir = serial_port_in(port, UART_IIR);

	ret = serial8250_handle_irq(port, iir);

	/*

	 * It is possible that RX TIMEOUT is signalled after FIFO

	 * has been drained, in which case a dummy read of RX FIFO is

	 * required to clear RX TIMEOUT condition.

	 */

	if ((iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT) {

		if (serial_port_in(port, UART_OMAP_RX_LVL) == 0)

			serial_port_in(port, UART_RX);

	}

	serial8250_rpm_put(up);



	return IRQ_RETVAL(ret);