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How to understand the meaning of inbound and outbound about PCIE?

steve zhang
Expert 1690 points

Hi everyone:

Recently ,I need to use PCIE in my daily work.And I had saw some reference material.But

I cannot understand the meaning of inbound and outbound all the time.

In my opinion, For the same PCIE visit or access,you can say inbound and you also say outbound

too.

For example,Now I suppose RC(played by PC linux host)  access EP (played by DSP c6678) via PCIE.

According to one of the reference material I found in google below:

I think I can say this access belongs to inbound and I also can say this access belongs to outbound.

it's all decided from which side.

1.From PC host RC side

According to the above reference material ,PC host RC can be considered as the local device.

and DSP c6678 EP can be considered as the external device.So the access initiates by local device

_PC host linux RC. Of courese this situation belongs to outbound .

2.From the 6678  DSP  EP side

Also on the basis of reference material above.

We also can consider the ep or dsp or c6678 as the local device and consider PC or HOST linux or

RC  as the external device.On this case.We can said that the external device initiates the access or

read/write operation.If this so,We of course definitely consider this situation as inbound.

So the conclusion like this:

I think wherever it can be considered as inbound or outbound is decided that

who is local device and who is the external device.

Because from different side or view.That question have different answers.

That's the reason that I consider you can say it belongs to inbound and also

can say it belongs to outbound.

Do you agree with me?  Any advice will be appreciated.

Best Regards!

  • 0
    TI__Mastermind 18146 points

    Hi,

    Inbound address translation is used to remap accepted incoming accesses from other
    PCIe devices to locations within the device's memory map.


    Outbound Address Translation maps internal bus address to PCIe address space. This is accomplished by using outbound address translation logic. For each outbound read/write request, the address translation module within the PCIESS can convert an internal bus address to a PCIe address of memory read/write type.

    See also the PCIe Users Guide:

    http://www.ti.com/litv/pdf/sprugs6d

    Kind regards,

    one and zero

  • 0 in reply to one and zero
    TI__Guru* 95265 points

    To avoid those confusions of inbound/outbound terms, it good to understand the how PCIE read/write works and how address is translated. You can read the same document sprabk8 examples 1,2,3,4.

    Regards, Eric