Re: [Ltib] mpc8349emitx.dts device tree entry for pci bridge

[Stuart Hughes]

Hi Steve,

I think you'll need help from one of the ppc kernel developers lists for
this one.

BTW: please join the list http://lists.nongnu.org/mailman/listinfo/ltib
if you want your messages to get through without moderation.

Regards, Stuart


On Sun, 2008-12-07 at 09:01 -0800, Steve DeLaney wrote:
> Hi there, not sure if this is the right forum for this topic but here goes.
> 
> We made a kernel update for MPC8349E LTIB to 2.6.25 to support a 
> PCI board.  The board is designed as "bridge behind bridge", in other
> words there is a PLX PCI bridge chip, behind which lies a vendor chip.  The 
> chip enumerates as a bridge, and also asserts INTA in its PCI config PINS.
> With the PCI board in the full size slot 1, the scheme is like this:
> 
> 
>                  IRQ20
>                    ^
> mpc8349e pci1      |
> ------------       |
>   plx bridge       |
>   ------------   INTA
>     vendor chip ---^
> 
> 
> The problem we are seeing is the IRQ granted to the board is IRQ 0,
> and it appears that the device tree process is unable to process a 
> board of this sort (under arch/powerpc/kernel/prom_parse.c) 
> 
> As a point of reference we have a success case
> on a USB card that does grant INTA on IRQ 20.   But that USB card is
> an end node controller device, not a bridge.
> 
> We think the best solution to this is probably to add a device tree entry
> to describe our more complex PCI bridge board.  
> Documentation/powerpc/booting-without-of.txt is a good start but 
> its not so obvious how to add such an entry to the device tree.
> We were hoping to see if someone could point
> us to a example to a similar device tree bridge description? 
> 
> Cheers!
> 
> /steverino2
> 
> 
> 
> 
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