Commit 1fe0e1fa authored by Tony Lindgren's avatar Tony Lindgren Committed by Greg Kroah-Hartman
Browse files

serial: 8250_omap: Handle optional overrun-throttle-ms property 



Handle optional overrun-throttle-ms property as done for 8250_fsl in commit
6d7f677a ("serial: 8250: Rate limit serial port rx interrupts during
input overruns"). This can be used to rate limit the UART interrupts on
noisy lines that end up producing messages like the following:

ttyS ttyS2: 4 input overrun(s)

At least on droid4, the multiplexed USB and UART port is left to UART mode
by the bootloader for a debug console, and if a USB charger is connected
on boot, we get noise on the UART until the PMIC related drivers for PHY
and charger are loaded.

With this patch and overrun-throttle-ms = <500> we avoid the extra rx
interrupts.

Cc: Carl Philipp Klemm <philipp@uvos.xyz>
Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: default avatarTony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20210727103533.51547-2-tony@atomide.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1a191ddc

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

+24 −1
Original line number Diff line number Diff line
@@ -617,7 +617,7 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id) 
	struct uart_port *port = dev_id;

	struct omap8250_priv *priv = port->private_data;

	struct uart_8250_port *up = up_to_u8250p(port);

	unsigned int iir;

	unsigned int iir, lsr;

	int ret;



#ifdef CONFIG_SERIAL_8250_DMA
@@ -628,6 +628,7 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id) 
#endif



	serial8250_rpm_get(up);

	lsr = serial_port_in(port, UART_LSR);

	iir = serial_port_in(port, UART_IIR);

	ret = serial8250_handle_irq(port, iir);
@@ -642,6 +643,24 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id) 
		serial_port_in(port, UART_RX);

	}



	/* Stop processing interrupts on input overrun */

	if ((lsr & UART_LSR_OE) && up->overrun_backoff_time_ms > 0) {

		unsigned long delay;



		up->ier = port->serial_in(port, UART_IER);

		if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {

			port->ops->stop_rx(port);

		} else {

			/* Keep restarting the timer until

			 * the input overrun subsides.

			 */

			cancel_delayed_work(&up->overrun_backoff);

		}



		delay = msecs_to_jiffies(up->overrun_backoff_time_ms);

		schedule_delayed_work(&up->overrun_backoff, delay);

	}



	serial8250_rpm_put(up);



	return IRQ_RETVAL(ret);
@@ -1353,6 +1372,10 @@ static int omap8250_probe(struct platform_device *pdev) 
		}

	}



	if (of_property_read_u32(np, "overrun-throttle-ms",

				 &up.overrun_backoff_time_ms) != 0)

		up.overrun_backoff_time_ms = 0;



	priv->wakeirq = irq_of_parse_and_map(np, 1);



	pdata = of_device_get_match_data(&pdev->dev);