[PATCH] serial: liteuart: polling all interrupts in the IRQ process

[PATCH] serial: liteuart: polling all interrupts in the IRQ process

[Inochi Amaoto]

When using liteuart with aplic and imsic, the new interrupt will lost
if the interrupt handler can not handle all the data. This is simply
because the interrupt line will never be low, and the aplic will not
send the interrupt to imsic again.

Handle all data in the IRQ handler until no data incoming.

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
---
 drivers/tty/serial/liteuart.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
index 6429e8f11f36..436e8f06fb75 100644
--- a/drivers/tty/serial/liteuart.c
+++ b/drivers/tty/serial/liteuart.c
@@ -140,11 +140,17 @@ static irqreturn_t liteuart_interrupt(int irq, void *data)
 	 * irq[save|restore] spin_lock variants to cover all possibilities
 	 */
 	uart_port_lock_irqsave(port, &flags);
-	isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
-	if (isr & EV_RX)
-		liteuart_rx_chars(port);
-	if (isr & EV_TX)
-		liteuart_tx_chars(port);
+
+	isr = litex_read8(port->membase + OFF_EV_PENDING);
+
+	while (isr & uart->irq_reg) {
+		if (isr & EV_RX)
+			liteuart_rx_chars(port);
+		if (isr & EV_TX)
+			liteuart_tx_chars(port);
+		isr = litex_read8(port->membase + OFF_EV_PENDING);
+	}
+
 	uart_port_unlock_irqrestore(port, flags);
 
 	return IRQ_RETVAL(isr);
-- 
2.51.0

Re: [PATCH] serial: liteuart: polling all interrupts in the IRQ process

[Inochi Amaoto]

On Tue, Aug 26, 2025 at 04:14:44PM +0800, Inochi Amaoto wrote:
> When using liteuart with aplic and imsic, the new interrupt will lost
> if the interrupt handler can not handle all the data. This is simply
> because the interrupt line will never be low, and the aplic will not
> send the interrupt to imsic again.
> 
> Handle all data in the IRQ handler until no data incoming.
> 
> Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
> ---
>  drivers/tty/serial/liteuart.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> index 6429e8f11f36..436e8f06fb75 100644
> --- a/drivers/tty/serial/liteuart.c
> +++ b/drivers/tty/serial/liteuart.c
> @@ -140,11 +140,17 @@ static irqreturn_t liteuart_interrupt(int irq, void *data)
>  	 * irq[save|restore] spin_lock variants to cover all possibilities
>  	 */
>  	uart_port_lock_irqsave(port, &flags);
> -	isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
> -	if (isr & EV_RX)
> -		liteuart_rx_chars(port);
> -	if (isr & EV_TX)
> -		liteuart_tx_chars(port);
> +
> +	isr = litex_read8(port->membase + OFF_EV_PENDING);
> +
> +	while (isr & uart->irq_reg) {
> +		if (isr & EV_RX)
> +			liteuart_rx_chars(port);
> +		if (isr & EV_TX)
> +			liteuart_tx_chars(port);
> +		isr = litex_read8(port->membase + OFF_EV_PENDING);
> +	}
> +
>  	uart_port_unlock_irqrestore(port, flags);
>  
>  	return IRQ_RETVAL(isr);
> -- 
> 2.51.0
> 

Just ignore this patch. The problem is caused by our incorrect
hardware implementation. And everything works fine as the hardware
is fixed.

Regards
Inochi