Re: [PATCH v5 0/2] PCI: mediatek-gen3: Add 2-lanes mode support + clock

On Fri, Aug 7, 2026 at 11:21 PM Bjorn Helgaas <[email protected]> wrote:
>
> On Fri, Aug 07, 2026 at 11:24:09AM +0800, Chen-Yu Tsai wrote:
> > On Fri, Aug 7, 2026 at 12:53 AM Christian Marangi <[email protected]> wrote:
> > > This small series introduce support for 2-lanes mode for Airoha AN7581
> >
> > Just a nitpick, but I would probably name this something else, like
> > "cross-controller lane-bonding mode" or "lane stealing"? PCIe already
> > has 2x lanes as a standard feature, so this naming is a bit confusing.
> > It's not like dual-LVDS display in which LVDS is only a single lane.
>
> I suggested the "2-lane" and "x2" terminology because I assumed the
> result is what the PCIe spec would describe as a "x2 Link" consisting
> of two Lanes.
>
> If that's not the case, maybe "cross-controller lane-bonding mode" or
> "lane stealing" would be more accurate, but I don't know what those
> mean, so if we use them I would also like to know what the result
> looks like in standard PCIe terms.

Benjamin pointed out later in the thread that it is just bifurcation.

I would assume "PCIe bifurcation" is a standard term, so maybe we could
call this "Support un-bifurcated 2-lane operation"?

On the implementation side, having to reach into the second PCIe controller
is a bit messy :(


ChenYu

> > > SoC. This is needed for correctly functionality of Eagle WiFi Card
> > > normally attached to this SoC that require a 2-line PCIe card to
> > > correctly work (and give the proper performance)
> > >
> > > The first 2 patch address a limitation of the PCIe implementation
> > > where the PERSTOUT reset were indirectly asserted and deasserted
> > > all at the same time (for all the 3 PCIe card) with PCIe
> > > enable and disable.
> > > The 2 patch address this and introduce correct reset to control
> > > reset line for the relevant PCIe line.
> > >
> > > The last 2 patch add additional logic and support to assert
> > > and deassert the PERSTOUT and also apply the required configuration
> > > for 2-lanes mode.
> > >
> > > 2-lanes mode is implemented in DT by adding the required property
> > > and by defining the "num-lanes" to 2.