Linux/AM4379: Can not set GPIO value

Tool/software: Linux

Hi:

 I am using a am4379 processor,  in my peoject i need  to use some gpiointerface,

The tools that I am using:

ti-processor-sdk-linux-am437x-evm-01.00.00.03

linux-3.14.43

and i had config those interface in am4379-gp-evm.dts:

&gpio0 {	
	status = "okay";


	p23 {
		gpio-hog;
		gpios = <23 GPIO_ACTIVE_HIGH>;
		/* SelEMMCorNAND selects between eMMC and NAND:
		 * Low: NAND
		 * High: eMMC
		 * When changing this line make sure the newly
		 * selected device node is enabled and the previously
		 * selected device node is disabled.
		 */
		output-low;
		line-name = "SelEMMCorNAND";
	};

};

&gpio1 {
	status = "okay";
};
&gpio2 {
	status = "okay";
};

&gpio3 {
	status = "okay";
};

&gpio4 {
	status = "okay";
};

&gpio5 {	
	status = "okay";
};

 after i compile the kernel and star form microSD，see logs find ：

[    0.164395] OMAP GPIO hardware version 0.1

and open /sys/class/gpio can find  the gpio had exist:

root@am437x-evm:~# cd /sys/class/gpio/
root@am437x-evm:/sys/class/gpio# ls
export gpiochip128 gpiochip32 gpiochip96
gpiochip0 gpiochip160 gpiochip64 unexport

and i can use "echo N >  export " export gpio interface , set  gpio direction,set gpio value ,cat  direction and cat value is correct,

root@am437x-evm:/sys/class/gpio# echo 134 > export 
root@am437x-evm:/sys/class/gpio# cd gpio134
root@am437x-evm:/sys/class/gpio/gpio134# echo out > direction 
root@am437x-evm:/sys/class/gpio/gpio134# cat direction 
out
root@am437x-evm:/sys/class/gpio/gpio134# echo 1 > value 
root@am437x-evm:/sys/class/gpio/gpio134# cat value 
1
root@am437x-evm:/sys/class/gpio/gpio134#

but when i use oscilloscope  measuerment  gpio can not  find signal out , i use CCS and XDS200 emulator check config find the export and direction had set correct ,the value not set correct,

who can tell me where something wrong, thanks.