From: Tony Lindgren tony@atomide.com
[ Upstream commit 1fe0e1fa3209ad8e9124147775bd27b1d9f04bd4 ]
Handle optional overrun-throttle-ms property as done for 8250_fsl in commit 6d7f677a2afa ("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: Tony Lindgren tony@atomide.com Link: https://lore.kernel.org/r/20210727103533.51547-2-tony@atomide.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/8250/8250_omap.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index 95e2d6de4f21..cd85491a52f9 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -604,7 +604,7 @@ 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 @@ -615,6 +615,7 @@ 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);
@@ -629,6 +630,24 @@ 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); @@ -1345,6 +1364,10 @@ 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);