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Groups > comp.os.linux.hardware > #3290 > unrolled thread

Difference between PCIe host bridge and PCI-PCI bridge

Started byTan <tanmayinamdar@gmail.com>
First post2017-05-26 11:15 -0700
Last post2018-02-28 06:46 -0800
Articles 3 — 3 participants

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  Difference between PCIe host bridge and PCI-PCI bridge Tan <tanmayinamdar@gmail.com> - 2017-05-26 11:15 -0700
    Re: Difference between PCIe host bridge and PCI-PCI bridge Clemens Ladisch <clemens@ladisch.de> - 2017-06-03 19:01 +0200
    Re: Difference between PCIe host bridge and PCI-PCI bridge Zihan <whois.zihan.yang@gmail.com> - 2018-02-28 06:46 -0800

#3290 — Difference between PCIe host bridge and PCI-PCI bridge

FromTan <tanmayinamdar@gmail.com>
Date2017-05-26 11:15 -0700
SubjectDifference between PCIe host bridge and PCI-PCI bridge
Message-ID<47eeec51-0367-4528-bb06-83502d76f104@googlegroups.com>
Hi,

I would appreciate if someone explains the difference between PCIe host bridge and PCI-PCI bridge on Intel platforms.

On Intel systems, I see that there is only one Host Bridge and multiple PCI-PCI bridges. When I dump the config spaces, I found that PCI-PCI bridges have Header Type '1' while Host Bridge have header type '0'. As per my understanding, only non Bridge devices support header type '0'.

Thanks,
Tan

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#3291

FromClemens Ladisch <clemens@ladisch.de>
Date2017-06-03 19:01 +0200
Message-ID<epg8ffFrivmU1@mid.individual.net>
In reply to#3290
Tan wrote:
> I would appreciate if someone explains the difference between PCIe host
> bridge and PCI-PCI bridge on Intel platforms.

PCI/PCI bridges are interfaces between two PCI buses.
The host bridge (or root complex) is the interface between the top-level
PCI bus and the CPU (the host).

> I found that PCI-PCI bridges have Header Type '1' while Host Bridge
> have header type '0'. As per my understanding, only non Bridge devices
> support header type '0'.

From the point of view of the PCI bus, the host is not visible as a PCI
device, so the device called "host bridge" is not actually a bridge.


Regards,
Clemens

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#3313

FromZihan <whois.zihan.yang@gmail.com>
Date2018-02-28 06:46 -0800
Message-ID<3dcb834b-9698-4ea4-add1-790da6c41ba9@googlegroups.com>
In reply to#3290
Nice explanation, but I wonder what is the situation when I have multiple PCI segment(domain)?

Suppose I setup 3 PCI domains, do I have 3 Root Bridges in a single Host Bridge, or do I have 3 Host Bridges? In either case, do theses bridges share a common south bridge, or they have their own ones?

Please correct me if I'm wrong as I just start to learn PCI(e).

Thanks.

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