Problem of using mmap() to map GPIO registers

ZIYANG YE

Intellectual 360 points

Other Parts Discussed in Thread: 66AK2E05

Hi,

I am using 66AK2E05,and try to map the GPIO registers to user space.

According to the related Docs,I get the information below:

So I try to map 0x0260BF00 + 0x0010 for the GPIO Direction Register,

Here is how I do it:

But this is what I got while running it:

If I try to map aemif@30000000,no error occurs.

Any help on this will be appreciated!

Regards,

kevin

over 10 years ago

0 Titusrathinaraj Stalin over 10 years ago

TI__Guru** 116100 points

Hi kevin,
Can you please try "int" instead of "char" with error checking ?
Also use "*(map_base+i)" for accessing.

Ex:
int *map_base = NULL;

map_base = (int *) mmap(NULL, MAP_SIZE,PROT_READ|PROT_WRITE, MAP_SHARED, dev_fd, GPIO_REG_BASE);

if (map_base == MAP_FAILED) {
perror("Map failed; Can't map");
return -1;
}

printf("content: 0x%x\n",*(map_base+i));

0 ZIYANG YE over 10 years ago in reply to Titusrathinaraj Stalin

Intellectual 360 points

Hi Titus S,

Sure, I changed the code using your method,

but the result looks the same:

Could you clarify that my mapping address is correct?

#define GPIO_REG_BASE 0x0260BF00 + 0x0010

Because it works while the address is changed to 0x30000000 (EMIF)

Thank you!

Regards,

kevin

0 Titusrathinaraj Stalin over 10 years ago in reply to ZIYANG YE

TI__Guru** 116100 points

Hi Kevin,
Can you please use the following MAP SIZE ?

#define MAP_SIZE 0x30

0 Raja over 10 years ago

TI__Guru* 81335 points

Hi Kevin,

I do not understand the purpose of this driver. Have you removed the GPIO support form kernel device tree? If no, please follow general way of accessing the GPIO from linux user space.

The user can access GPIO either command line or user programming, both were explained.

http://falsinsoft.blogspot.com/2012/11/access-gpio-from-linux-user-space.html

Thank you.

0 ZIYANG YE over 10 years ago in reply to Titusrathinaraj Stalin

Intellectual 360 points

Hi Titus S,

I try to use 0x30 or even smaller size,but still getting the Segmentation fault error:

Thank you!

Regards,

kevin

0 ZIYANG YE over 10 years ago in reply to Raja

Intellectual 360 points

Hi Rajasekaran K,

Thanks for you reply!

For now,I know how to opera GPIOs in user space,

but as part of my learning, I am trying to changed the registers myself,

Do I have to disable the whole GPIO support on kernel to access the registers?

Regards,

kevin

0 Raja over 10 years ago in reply to ZIYANG YE

TI__Guru* 81335 points

Hi Kevin,
If you have issues with it. Please disable the GPIO support form device tree and try.

Thank you.

0 ZIYANG YE over 10 years ago in reply to Raja

Intellectual 360 points

Hi Rajasekaran K,

Thank you for the advice!

Regards,
kevin

Processors

Processors forum

Problem of using mmap() to map GPIO registers