[coreboot] unexpected exception errors loading vga rom

Joseph Smith joe at settoplinux.org
Thu Apr 30 17:41:12 CEST 2009

On Thu, 30 Apr 2009 07:55:24 -0700, ron minnich <rminnich at gmail.com> wrote:
> On Thu, Apr 30, 2009 at 5:37 AM, Joseph Smith <joe at settoplinux.org>
>> Well, along the way I did learn a lot more about irq tables. Like each
> line
>> in irq_tables.c is not actually a device but a route to the device/s.
> There
>> can be multiple devices on a route. For example all of my USB devices
> are
>> on the same route:
> I think this is a mistinterpretaion. In PCI-speak, there is one
> device. Each device has several functions.
> A device itself has only one wire -- there is one physical wire for
> that chip or device. It is called the interrupt line.
> For reasons too long to go into here (basically, the PCI SIG made a
> slight mistake in designing interrupts) we need to have the
> IRQ table so we know mapping of IRQ wire from device to IRQ wire of
> bus/interrupt router, e.g. INTA of a chip/device may map to INTC of
> the bus and hence the interrupt router.
>>                       |- USB #1        |- USB #2    
>  |- USB #3       |-
>> {0x00,(0x1d<<3)|0x0, {{0x60, 0x1ef8}, {0x63, 0x1ef8}, {0x62, 0x1ef8},
>> {0x6b, 0x01ef8}}, 0x0, 0x0},
>> is the same as:
>> {0x00,(0x1d<<3)|0x0, {{0x60, 0x1ef8}, {0x00, 0x0000}, {0x00, 0x0000},
>> {0x00, 0x00000}}, 0x0, 0x0}, /* [A] USB UHCI 1 */
>> {0x00,(0x1d<<3)|0x1, {{0x60, 0x1ef8}, {0x63, 0x1ef8}, {0x00, 0x0000},
>> {0x00, 0x00000}}, 0x0, 0x0}, /* [B] USB UHCI 2 */
>> {0x00,(0x1d<<3)|0x2, {{0x60, 0x1ef8}, {0x63, 0x1ef8}, {0x62, 0x1ef8},
>> {0x00, 0x00000}}, 0x0, 0x0}, /* [C] USB UHCI 3 */
>> {0x00,(0x1d<<3)|0x7, {{0x60, 0x1ef8}, {0x63, 0x1ef8}, {0x62, 0x1ef8},
>> {0x6b, 0x01ef8}}, 0x0, 0x0}, /* [D] EHCI */
> no, not really. Functions don't have interrupts. The device itself has
> an interrupt.
>> I never really understood this until now. Also the "bus, dev|fn," can be
>> diseaving becuase it only tells you the first device on the route INTA.
> It tells you about that device. Those other things you mentioned are
> functions of that device.
>> If no one objects I would really like to add a section to the
>> http://www.coreboot.org/Creating_Valid_IRQ_Tables page breaking down
>> irq_tables.c and explaining what each part means. I think this would
> help
>> people understand this very confusing process a little more.
> I think your explanation is not really correct; you might want to
> re-read the spec fot that table to see what it's about. As it is
> you're going to confuse people :-)
> I made this mistake myself on geode once before marc pointed it out to
> I will be glad when this aspect of PCI is gone.

Me too! Now you got me really confused just when I thought I had finally
figured it out :-(
Can you point me to some good reference docs then?
Joseph Smith

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