IO APIC read write inconsistent problem

yuq · **Joined:** Tue Jan 11, 2011 2:06 am **Posts:** 17

Hi, guys. I'm writing IOAPIC code. I follow every guide I can get but I have some problem:
I write 0x0100000000000022 to IOAPIC redirect table register pin2, it seems work because the CPU get correct interrupt. But when I read it out, it becomes 0x0010000000100000 0x0000002200000022, the value shift to pin3 and double the first 32bit value. If I read the value twice, it won't shift to pin3 but still double 32bit.
My code:

Code:

static inline unsigned int ioapic_read(unsigned int reg)
{
    writel(IOAPIC_BASE+IOAPIC_IOREGSEL, reg);
    return readl(IOAPIC_BASE+IOAPIC_IOWIN);
}

static inline void ioapic_write(unsigned int reg, unsigned int value)
{
    writel(IOAPIC_BASE+IOAPIC_IOREGSEL, reg);
    writel(IOAPIC_BASE+IOAPIC_IOWIN, value);
}

uint64_t get_ioapic_entry(int irq)
{
    uint64_t ret;

    ret = ioapic_read(IOAPIC_IOREDTBL + 2*irq + 1);
    ret <<= 32;
    ret |= ioapic_read(IOAPIC_IOREDTBL+2*irq);
    return ret;
}

void set_ioapic_entry(int irq, int level, int share)
{
    unsigned int h, l;

    // if share is true, broadcast the interrupt
    if (share)
   h = 0xff000000;
    else
   h = 0x01000000;

    // physical destination mode, fixed delivery mode
    if (level)
   l = 0x0000a000;
    else
   l = 0;

    ioapic_write(IOAPIC_IOREDTBL + 2*irq + 1, h);
    ioapic_write(IOAPIC_IOREDTBL + 2*irq, l + T_IRQ + irq);
}

the print code:
 cprintf("\n======== IOAPIC interrupt redirect table =========\n");
    for (i=0; i<24; i++) {
   //get_ioapic_entry(i);
   //get_ioapic_entry(i);
   cprintf("%02d:%016llx ", i, get_ioapic_entry(i));
   if (((i+1)%4) == 0)
       cprintf("\n");
    }

help me!!

EDIT: Brendan added code tags..

yuq · **Joined:** Tue Jan 11, 2011 2:06 am **Posts:** 17

I find why:
the writel and readl inline function is optimized by gcc.

Code:

static __inline uint32_t readl(uint32_t addr)
{
    return *(uint32_t *)(addr);
}
static __inline void writel(uint32_t addr, uint32_t data)
{
    *(uint32_t *)(addr) = data;
}

I'm trying to find how to volatile this.

EDIT: Brendan added code tags

Darwish · **Joined:** Sat Oct 17, 2009 4:32 am **Posts:** 21

yuq wrote:

I find why:
the writel and readl inline function is optimized by gcc.
...
I'm trying to find how to volatile this.

The wiki doesn't bite; what you need to know is already covered in the Apic article. Good luck.

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IO APIC read write inconsistent problem

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