Commit 8d17dc05 authored by Tapio Reijonen's avatar Tapio Reijonen Committed by Greg Kroah-Hartman
Browse files

serial: max310x: improve interrupt handling 



When there is a heavy load of receiving characters to all
four UART's, the warning 'Hardware RX FIFO overrun' is
sometimes detected.
The current implementation always service first the highest UART
until no more interrupt and then service another UART
(ex: UART3 will be serviced for as long as there are interrupts
for it, then UART2, etc).

This commit handle all individual interrupt sources before
reading the global IRQ register again.

This commit has also a nice side-effect of improving the efficiency
of the driver by reducing the number of reads of the global
IRQ register.

Signed-off-by: default avatarTapio Reijonen <tapio.reijonen@vaisala.com>
Reviewed-by: default avatarJiri Slaby <jirislaby@kernel.org>
Reviewed-by: default avatarHugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20250908-master-max310x-improve-interrupt-handling-v3-1-91985e82ba39@vaisala.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent fc702e7d

drivers/tty/serial/max310x.c

+17 −6
Original line number Diff line number Diff line
@@ -823,17 +823,28 @@ static irqreturn_t max310x_ist(int irq, void *dev_id) 
	bool handled = false;



	if (s->devtype->nr > 1) {

		bool done;



		do {

			unsigned int val = ~0;

			unsigned long irq;

			unsigned int port;



			done = true;



			WARN_ON_ONCE(regmap_read(s->regmap,

						 MAX310X_GLOBALIRQ_REG, &val));

			val = ((1 << s->devtype->nr) - 1) & ~val;

			if (!val)

				break;

			if (max310x_port_irq(s, fls(val) - 1) == IRQ_HANDLED)



			irq = val;



			for_each_clear_bit(port, &irq, s->devtype->nr) {

				done = false;



				if (max310x_port_irq(s, port) == IRQ_HANDLED)

					handled = true;

		} while (1);

			}



		} while (!done);

	} else {

		if (max310x_port_irq(s, 0) == IRQ_HANDLED)

			handled = true;