p2a control driver

[Patrick Venture]

On Thu, Jun 11, 2020 at 7:35 AM Montag, Gil <gil.montag at intel.com> wrote:
>
> Hi Patrick,
>
>
>
> I have an AST2500 BMC in my system.
>
> Doing lspci on the host connected to it via PCIe shows:
>
>
>
> 0e:00.0 PCI bridge: ASPEED Technology, Inc. AST1150 PCI-to-PCI Bridge (rev 04) (prog-if 00 [Normal decode])
>
>         Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
>
>         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
>
>         Latency: 0, Cache Line Size: 64 bytes
>
>         Interrupt: pin A routed to IRQ 17
>
>         Bus: primary=0e, secondary=0f, subordinate=0f, sec-latency=32
>
>         I/O behind bridge: 0000e000-0000efff
>
>         Memory behind bridge: f6000000-f70fffff
>
>         Prefetchable memory behind bridge: 00000000fff00000-00000000000fffff
>
>         Secondary status: 66MHz+ FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- <SERR- <PERR-
>
>         BridgeCtl: Parity- SERR+ NoISA- VGA- MAbort- >Reset- FastB2B-
>
>                 PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-
>
>         Capabilities: <access denied>
>
>
>
> This PCI-PCI bridge is shown regardless of the aspeed-p2a-ctrl driver loaded or not.
>
> Is this the bridge you refer in your patch https://patchwork.kernel.org/patch/10873949/  or should I see some downstream PCI-AHB bridge other than this one?

The bridge is handled through MMIO, it's not specifically a bridge
device, and the driver configures the PCI-to-AHB MMIO bridge - the PCI
bridge itself exists regardless depending on the configuration.  If
that makes sense.

>
> If I should see such PCI-AHB bridge, what do I need to do to really see it?

The bridge is controlled from the host side with a register in BAR0,
and from the BMC via the control registers.

https://github.com/openbmc/phosphor-ipmi-flash/tree/master/tools <--
this handles identifying the bridge from the host-side.

>
>
>
> Thank you
>
> Gil
>
>
>
>
>
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