* [PATCH 2/2] serial: 8250_omap: Handle optional overrun-throttle-ms property
2021-07-27 10:35 [PATCH 1/2] dt-bindings: serial: 8250: Update for standard overrun-throttle property Tony Lindgren
@ 2021-07-27 10:35 ` Tony Lindgren
2021-08-02 20:10 ` [PATCH 1/2] dt-bindings: serial: 8250: Update for standard overrun-throttle property Rob Herring
1 sibling, 0 replies; 3+ messages in thread
From: Tony Lindgren @ 2021-07-27 10:35 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Vignesh Raghavendra, linux-serial, linux-omap, linux-kernel,
Carl Philipp Klemm, Merlijn Wajer, Pavel Machek,
Sebastian Reichel
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>
---
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
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -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);
--
2.32.0
^ permalink raw reply [flat|nested] 3+ messages in thread