[Onion Omega2] Direct GPIO register access problem

Krzysztof Skiba

Hello everyone.
I have some problems with my Onion. I'm trying to access device registers via mmap function. I've successfully map PWM registers (address: 0x10005000). I can write and read from these registers.
But when I try to change address to 0x10000600 (GPIO access registers) with the same code I can read, but write fails with message Segmentation fault.
I tried to unload all GPIO modules with no effect.
Here is my code (without headers):

int main(int argc, char *argv[])
{

uint32_t alloc_mem_size, page_mask, page_size;
volatile uint32_t *mem_pointer, *virt_addr;
const uint32_t mem_address = 0x10000600;
const uint32_t mem_size = 0x600;
page_size = 4096;

alloc_mem_size = (((mem_size / page_size) + 1) * page_size);
page_mask = (page_size - 1);

int mem_dev = open("/dev/mem", O_RDWR | O_SYNC);
mem_pointer = mmap(NULL,
               alloc_mem_size,
               PROT_READ | PROT_WRITE,
               MAP_SHARED,
               mem_dev,
               (mem_address & ~page_mask)
               );


virt_addr = (mem_pointer + (mem_address & page_mask)); 

int i=0;
close(mem_dev);
printf("Memory dump before\n");
for(i=0; i<10;i=i+2) 
{
	printf("GPIO memory address=0x%016x: 0x%016x\n", virt_addr+i, *(virt_addr+i));
}





// Set GPIO_0 direction bit
 (*(virt_addr))|=(1<<0);

printf("Memory dump after\n");
for(i=0; i<10;i=i+2) 
{
	printf("GPIO memory address=0x%016x: 0x%016x\n", virt_addr+i, *(virt_addr+i));
}

}

Help please

Patryk Wychowaniec

Where did you get the 0x10000600 number from?

Take a look at my GPIO management code:
https://github.com/Patryk27/Omega2-GPIO/blob/master/gpio.h

Krzysztof Skiba

@Krzysztof-Skiba said in [Onion Omega2] Direct GPIO register access problem:

x10000600

I found in Mediatek MT7688 Datasheet page 109:
https://labs.mediatek.com/en/download/50WkbgbH

"Module name: GPIO Base address: (+10000600h)"

Edit: Got it! Seems that datasheet info is incorrect.

Thanks for help!

volkan ünal

@Patryk-Wychowaniec Hi Patryk , when i look into the datasheet , i see this adress for GPIO_CTRL_0 32

10000600

How can you write your code ? any datasheet?

Patryk Wychowaniec

@volkan-ünal

Hi!

I have already responded you on GitHub, but to keep conversation here complete, I am also copy-pasting that response (https://github.com/Patryk27/Omega2-GPIO/issues/3) here:

I initially followed code written by the Omega team (https://github.com/OnionIoT/fast-gpio/blob/master/include/fastgpioomega2.h#L12) and I haven't really faced it with the documentation.

I believe the reason is that later we're doing a mmap call, which has to be page-aligned (which 0x10000600 is not), but it could be also a mistake in the MT7688's documentation.

Alex Costea

static const int REG_BLOCK_ADDR = 0x10000000;

static const int REGISTER_CTRL0_OFFSET = 384; // 32 bit reg offset !!!
static const int REGISTER_CTRL1_OFFSET = 385; // 32 bit reg offset !!! 
static const int REGISTER_CTRL2_OFFSET = 386; // 32 bit reg offset !!!

static const int REGISTER_DATA0_OFFSET = 392; // 32 bit reg offset !!!
static const int REGISTER_DATA1_OFFSET = 393; // 32 bit reg offset !!!
static const int REGISTER_DATA2_OFFSET = 394; // 32 bit reg offset !!!

static const int REGISTER_DSET0_OFFSET = 396; // 32 bit reg offset !!!
static const int REGISTER_DSET1_OFFSET = 397; // 32 bit reg offset !!!
static const int REGISTER_DSET2_OFFSET = 398; // 32 bit reg offset !!!

static const int REGISTER_DCLR0_OFFSET = 400; // 32 bit reg offset !!!
static const int REGISTER_DCLR1_OFFSET = 401; // 32 bit reg offset !!!
static const int REGISTER_DCLR2_OFFSET = 402; // 32 bit reg offset !!!

and then

Gpio::baseAddress = (uint32_t *) mmap(0, 1024, PROT_READ | PROT_WRITE, MAP_FILE | MAP_SHARED, memHandle,
                                      Gpio::REG_BLOCK_ADDR);

and then

void Gpio::writeToRegister(uint16_t registerOffset, uint32_t value) {
*(Gpio::baseAddress + registerOffset) = value;}

you are basically mapping to a 32 bit pointer...
so your offsets are in fact equivalent to the following address:

REGISTER_CTRL0_OFFSET = 384 (32 bit offset) -> hex(4384) = 0x600
REGISTER_CTRL1_OFFSET = 385 (32 bit offset) -> hex(4385) = 0x604
REGISTER_CTRL2_OFFSET = 386 (32 bit offset) -> hex(4*386) = 0x608

So the documentation is correct...
Be careful with pointer arithmetic...

Alex Costea

This post is deleted!

Alex Costea

@Krzysztof-Skiba said in [Onion Omega2] Direct GPIO register access problem:

virt_addr = (mem_pointer + (mem_address & page_mask));

this is wrong...

mem_pointer is already pointing to mem_address...

your line basically makes mem_pointer point to address

0x10000600 + (0x10000600*4 & page_mask) = .... SEG FAULT....

To Fix: change

const uint32_t mem_size = 0x600;

to

const uint32_t mem_size = 0x600+0xAC;

const uint32_t mem_address = 0x10000600;

to

const uint32_t mem_address = 0x10000000;

and

virt_addr = (mem_pointer + (mem_address & page_mask));

to

virt_addr = (mem_pointer + (mem_size/sizeof(uint32_t) );

volkan ünal

@Alex-Costea Thanks for reply , but i dont understand properly.
you mean that 384 (32 bit offset) -> hex(4384) = 0x600 , but how?

What about Gpio::baseAddress + registerOffset?