IBM OCP GPIO driver for linux 2.6

IBM OCP GPIO driver for linux 2.6

[Jean-Baptiste Maneyrol]

Hello everyone, I'm a newbie here!

I'm porting a custom PPC 405GP card based on a Walnut from Montavista
Linux 3.0 (kernel 2.4.18) to linux 2.6, and I was wondering if there is
a port of the IBM OCP GPIO driver (a char driver providing
device /dev/gpio, major 10 minor 185). The driver was written by Armin
Kuster, and it doesn't exist in the stock kernel 2.6.17.7.

Let me known if a port exists, or if there is a new way of accessing the
PPC 405GP GPIO under linux 2.6. Otherwise, I will port this driver using
the IBM IIC driver as an example (for the things about OCP). In this
case, do anybody know where I can have the last version of this driver
(I have v 1.7 (07/25/02)) ? 

Thanks for all!


Jean-Baptiste Maneyrol
Teamlog - France

Re: IBM OCP GPIO driver for linux 2.6

[Dale Farnsworth]

In article <1154603751.17247.10.camel@jb-portable> you write:
> I'm porting a custom PPC 405GP card based on a Walnut from Montavista
> Linux 3.0 (kernel 2.4.18) to linux 2.6, and I was wondering if there is
> a port of the IBM OCP GPIO driver (a char driver providing
> device /dev/gpio, major 10 minor 185). The driver was written by Armin
> Kuster, and it doesn't exist in the stock kernel 2.6.17.7.
> 
> Let me known if a port exists, or if there is a new way of accessing the
> PPC 405GP GPIO under linux 2.6.

The recommended way of accessing GPIO registers is to mmap them
and manipulate them directly in user space.

Below, I've included a quick hack that blinks a LED on a Walnut-like
board.

-Dale

#include <stdint.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>

#define GPIO_PAGE_ADDR	0xef600000

#define OUTPUT_REG	0x0700
#define TRISTATE_REG	0x0704
#define OPENDRAIN_REG	0x0718
#define INPUT_REG	0x071c

#define MEDIA_LED_BIT	0x20000000

#define reg_addr(p, o)	((uint32_t *)((void *)p + o))

int main(int argc, char *argv[])
{
	int i;
	uint32_t *p;
	char *filename = "/dev/mem";
	void *addr	= 0;
	size_t length	= 4096;
	int prot	= PROT_READ | PROT_WRITE;
	int flags	= MAP_SHARED;
	int fd		= open(filename, O_RDWR);
	off_t offset	= (off_t)GPIO_PAGE_ADDR;

	if (fd < 0) {
		perror("open");
		return 1;
	}

	p = mmap(addr, length, prot, flags, fd, offset);
	if (p == MAP_FAILED) {
		perror("mmap");
		return 4;
	}

	/* drive led output */
	*reg_addr(p, TRISTATE_REG) |= MEDIA_LED_BIT;

	/* blink media led 10 times */
	for (i = 0; i < 10; i++) {
		/* turn media led on */
		*reg_addr(p, OUTPUT_REG) &= ~MEDIA_LED_BIT;
		sleep(1);
		/* turn media led off */
		*reg_addr(p, OUTPUT_REG) |= MEDIA_LED_BIT;
		sleep(1);
	}

	return 0;
}

Re: IBM OCP GPIO driver for linux 2.6

[Arnd Bergmann]

On Thursday 03 August 2006 13:15, Jean-Baptiste Maneyrol wrote:
> Let me known if a port exists, or if there is a new way of accessing the
> PPC 405GP GPIO under linux 2.6. Otherwise, I will port this driver using
> the IBM IIC driver as an example (for the things about OCP). In this
> case, do anybody know where I can have the last version of this driver
> (I have v 1.7 (07/25/02)) ? 

The only OCP drivers that exist in the tree are for emac and iic.
Those will probably be converted to use something like of_platform_device
in the future, as soon as 4xx gets converted to arch/powerpc.

If you need to port the driver now, it's probably a good idea to use
a platform_driver instead of an ocp driver for it.

	Arnd <><

Re: IBM OCP GPIO driver for linux 2.6

[Milton Miller]

On Thu Aug  3 2006 08:53:00 AM CDT, Dale Farnsworth wrote:
> The recommended way of accessing GPIO registers is to mmap them
> and manipulate them directly in user space.

> 		/* turn media led on */
> 		*reg_addr(p, OUTPUT_REG) &= ~MEDIA_LED_BIT;
> 		sleep(1);
> 		/* turn media led off */
> 		*reg_addr(p, OUTPUT_REG) |= MEDIA_LED_BIT;

Very racy if you need different bits in the same word controlled by different programs.

milton