#To many interrupts from debug port rx line

##Problem description

The serial RX line (PA9/DRXD) is set by Linux without the pull-up internal resistor. This could cause a lot of receiving interrupts from
the debug serial port in noisy environments. 

##Solution

Change these lines in <i>arch/arm/boot/dts/at91sam9x5dtsi</i>:

Original

	/* shared pinctrl settings */
	dbgu {
		pinctrl_dbgu: dbgu-0 {
			atmel,pins =
				<AT91_PIOA 9 AT91_PERIPH_A AT91_PINCTRL_NONE		/* PA9 periph A */
				 AT91_PIOA 10 AT91_PERIPH_A AT91_PINCTRL_PULL_UP>;	/* PA10 periph A with pullup */
		};
	};

Changed

	/* shared pinctrl settings */
	dbgu {
		pinctrl_dbgu: dbgu-0 {
			atmel,pins =
				<AT91_PIOA 9 AT91_PERIPH_A AT91_PINCTRL_PULL_UP		/* PA9 periph A with pullup*/
				 AT91_PIOA 10 AT91_PERIPH_A AT91_PINCTRL_PULL_UP>;	/* PA10 periph A with pullup */
		};
	};

then compile the dts following this article:

* [Build linux kernel](/compile_linux_4_4)