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serial: 8250: 8250_omap: Fix possible interrupt storm

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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: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20210511151955.28071-1-vigneshr@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Vignesh Raghavendra 2021-05-11 20:49:55 +05:30 committed by Greg Kroah-Hartman
parent 1f06f5713f
commit 31fae7c8b1
1 changed files with 12 additions and 0 deletions
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12
drivers/tty/serial/8250/8250_omap.c
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@ -104,6 +104,9 @@
#define UART_OMAP_EFR2 0x23 #define UART_OMAP_EFR2 0x23
#define UART_OMAP_EFR2_TIMEOUT_BEHAVE BIT(6) #define UART_OMAP_EFR2_TIMEOUT_BEHAVE BIT(6)
/* RX FIFO occupancy indicator */
#define UART_OMAP_RX_LVL 0x64
struct omap8250_priv { struct omap8250_priv {
int line; int line;
u8 habit; u8 habit;
@ -625,6 +628,15 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
serial8250_rpm_get(up); serial8250_rpm_get(up);
iir = serial_port_in(port, UART_IIR); iir = serial_port_in(port, UART_IIR);
ret = serial8250_handle_irq(port, 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); serial8250_rpm_put(up);
return IRQ_RETVAL(ret); return IRQ_RETVAL(ret);