[microblaze-uclinux] GPIO LED heartbeat confusion

[Philipp Hachtmann <hachti@xxxxxxxxx>]

Hi folks,

I am using the Xilinx Spartan-3e 500 Board.

I wanted to use the GPIO_0 port and found out that my LEDs turn off 
automatically after a short while. And the xilinx_gpio driver itself 
looked innocent...

One grep and I found the following in

arch/microblaze/platform/microblaze-auto/machine.c:

>/* Function to drive one of the LED segments */
> void mach_heartbeat(unsigned int value)
> {
> 	/* 
> 	 * FIXME Strictly speaking this should probably be 
> 	 * protected by a semaphore 
> 	 */
>
> #ifdef CONFIG_XILINX_GPIO_0_INSTANCE
> 	/* Read current value on the port */
> 	volatile unsigned int cur_val = microblaze_gpio_read(CONFIG_XILINX_GPIO_0_BASEADDR);
>
> 	/* Clear LED bit  */
> 	cur_val &= ~0x00010000;
>
> 	/* Set it if required */
> 	if(value)
> 		cur_val |=  0x00010000;
> 	
> 	microblaze_gpio_write(CONFIG_XILINX_GPIO_0_BASEADDR,cur_val);
> #endif
> }

That could drive some people mad... Perhaps someone should add a config 
option to turn that on and off. Btw, my board's GPIO 0 has only 8 bits 
so I don't even see that there's something going on...

Best wishes,

Philipp
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