Re[2]: PCI Interrupt Binding

[PETE_HAWKINS@ziatech.com]

     >>>>>>>>>>>>>>>>>>>
     
Each PCI device can have upto 4 interrupt pins. If it is a single function 
device, it can have only one interrupt pin and this one pin is INTA#. A 
multi-funciton pci device may use all the interrupt pins, INTA#, INTB#, 
INTC# and INTD#. This naming is independent of any context: The designer of 
the chip decides which pin to be called what. And this naming will not 
change. When you say "INTA# pin of my chip", you always know what pin you 
are talking about and you know that no matter to what INT?# pin of the 
connector or of another pci device it is connected to, that pin, on your 
chip, is always called INTA#.
     
The device numbers that you have considered (device 0, the host -> bridge 
and device 1, the first PCI slot) are different from what is meant by device 
numbers in Section 11 of the pci to pci bridge spec. I have described the 
device numbers in this reply.
     
With the above in mind, the following is another presentation of devices 0 
through 4 of Table 9 in Section 11 of the pci to pci bridge spec. The 
followings are implied in that section:
     
1- The pci to pci bridge is on an add on card, and the add on card may be
   mounted on any slot
2- The primary interface of the bridge is connected to the connector 
3- The add on card contains at most 32 pci devices, numbered 0 to 31
4- These devices are connected to the secondary interface of the bridge
5- Table 9 only talks about routing the interrupt pins of these devices to 
the     interrupt pins of the connector and not about routing the interrupt 
pins of     the bridge to the connector.
6- It is not necessary for the bridge to perform this routing
     
In the following presentation of Table 9, which only shows devices 0 through 
4, the interrupt pins in one column belong to the device on the add on card 
except for the interrupt pins in the left most column which belong to the 
connector. 
The interrupt pins in one row are wired together. For instance, INTA# of 
Device 1 is wired to INTB# of Device 0 and they are wired to INTB# of the 
connector.
     
     
  C
  o      D      D      D      D      D 
  n      e      e      e      e      e 
  n      v      v      v      v      v 
  e      i      i      i      i      i 
  c      c      c      c      c      c 
  t      e      e      e      e      e 
  o
  r      0      1      2      3      4
     
INTA#  INTA#  INTD#  INTC#  INTB#  INTA#
     
INTB#  INTB#  INTA#  INTD#  INTC#  INTB#
     
INTC#  INTC#  INTB#  INTA#  INTD#  INTC#
     
INTD#  INTD#  INTC#  INTB#  INTA#  INTD#
     
     
If the bridge itself issues an interrupt, and the bridge is a single 
function pci device, it only has an INTA# interrupt pin. This pin should be 
connected to INTA# of the connector.
     
     
Hope this helps.
     
A. Najafi
     
     <<<<<<<<<<<<<<<<<<<<<<<<
     
     
     It looks to me like you got the rotation backwards.  According to the 
     P2P bridge spec, it should be:
     
     
     
     C
     o      D      D      D      D      D
     n      e      e      e      e      e 
     n      v      v      v      v      v 
     e      i      i      i      i      i 
     c      c      c      c      c      c 
     t      e      e      e      e      e
     o
     r      0      1      2      3      4
     
     INTA#  INTA#  INTB#  INTC#  INTD#  INTA#
     
     INTB#  INTB#  INTC#  INTD#  INTA#  INTB#
     
     INTC#  INTC#  INTD#  INTA#  INTB#  INTC#
     
     INTD#  INTD#  INTA#  INTB#  INTC#  INTD#
     
     
     The difference being the routing of the odd numbered devices.
     
     Pete Hawkins
     pete_hawkins@ziatech.com
(”„