Re: [PATCH v3] PCI: Add D3 support for PCI bridges in DT based platforms

Manivannan Sadhasivam
2024-02-27T17:08:50Z

On Tue, Feb 27, 2024 at 10:25:35AM -0600, Bjorn Helgaas wrote:

[...]

> > Ok, I got the issue. TBH, I added the device tree property based on
> > the existing quirks for the ACPI devices. But none of the DT based
> > platforms I'm aware of (even the legacy Qcom MSM8996 chipset
> > released in early 2016) doesn't have any issue with D3hot. But I'm
> > just nervous to assume it is the case for all the DT based platforms
> > in the wild.
> >
> > But to proceed further, what is your preference? Should we ammend
> > the DT property to make it explicit that the propery only focuses on
> > the D3hot capability of the bridge and it works as per the spec
> > (PMCSR) or bite the bullet and enable D3hot for all the non-ACPI
> > platforms?
> >
> > We can add quirks for the bridges later on if we happen to receive
> > any bug report.
>
> I would assume all devices support D3hot via PMCSR per spec. We can
> add quirks if we discover something that doesn't.
>

When you say "all devices", are you referring to bridges in DT platforms or the
bridges across all platforms?

- Mani

> If we add annotations that "this device works correctly", we're
> digging a hole for ourselves because it's impossible to remove those
> annotations and they complicate all future maintenance.
>
> Bjorn

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