Re: [PATCH 0/2] PCI: Fix ACS enablement for Root Ports in DT platforms

[Manivannan Sadhasivam]

On Thu, Sep 18, 2025 at 11:11:02AM -0300, Jason Gunthorpe wrote:
> On Wed, Sep 10, 2025 at 11:09:19PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> > This issue was already found and addressed with a quirk for a different device
> > from Microsemi with 'commit, aa667c6408d2 ("PCI: Workaround IDT switch ACS
> > Source Validation erratum")'. Apparently, this issue seems to be documented in
> > the erratum #36 of IDT 89H32H8G3-YC, which is not publicly available.
> 
> This is a pretty broken device! I'm not sure this fix is good enough
> though.
> 
> For instance if you reset a downstream device it should loose its RID
> and then the config cycles waiting for reset to complete will trigger SV
> and reset will fail?
> 

No. Resetting the Ethernet controller connected to the switch downstream port
doesn't fail and we could see that the reset succeeds.

Maybe the bus number was still captured by the device.

> Maybe a better answer is to say these switches don't support SV and
> prevent the kernel from enabling it in the first place?
> 

I'm not sure though, as Windows seem to be running fine just with this erratum,
without disabling SV.

- Mani

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