Thread: Linux Kernel Using ioremap().

This would be the reason that my brain was totally fried last night.

this would be an example of the code:

Code:

static void *mmio, *control;
int32_t register_my_system(MY_SYSTEM_USER *user)
{

        // request memory region is done at insmod time and _should_not_ be where the problem is.

        mmio = ioremap(0x080C0000, 0x100);

        control = mmio + 0x28;


        iowrite16(6, control);  // enables bits 2 and 3 (one of these is an IRQ enable)
        return 0;
}
EXPORT_SYMBOL(register_my_system);

void unregister_my_system(MY_SYSTEM_USER *user)
{
        iounmap(mmio);
        control = NULL;
        mmio = NULL;
}

Now, the issue is this: If I unregister_my_system then attempt to register_my_system I hang. Sometimes I get an error from the kernel:

Originally Posted by Linux Kernel

Unable to handle kernel paging request at virtual address 464c457f
pgd = c9f78000
[464c457f] *pgd=00000000Function entered at [<c0096c14>] from [<c0096cbc>]
r5:00000000 r4:00000002
Function entered at [<c0096c64>] from [<c0096d84>]
r8:c002e764 r7:00000005 r6:bebfbb74 r5:4001ce14 r4:00000000
Function entered at [<c0096d60>] from [<c002df60>]
Code: e597300c e1d320b0 e1a02a02 e1a02a22 (e18420b1)

but this is the ONLY thing I can get from it. The actual virtual address is 0xCAA6C028 and is that address each time I reboot and register with the driver.

So, my question is what could possibly be hanging the system? I have tried absolutely everything I can think of but still cannot figure this one out. Any help would be greatly appreciated.

Yes, that is an issue that I had to overcome. A hardware guy wrote the info on that one, but did lay out the bits in a table so that I know that bits 2 and 3 are actually 2^1 and 2^2 respectively.

ARM XScale.

Not only do I check for NULL, but I also have 30 different registers that I set. I have gone so far as to printk() each one to make sure that it is set. Also, I have some insane paranoia type if statements that test to be sure that each location is not NULL.

What can I same, I'm a safety boy.