On Mon, Apr 18, 2022 at 11:53 AM Bjorn Helgaas <[email protected]> wrote:
>
> On Sun, Apr 17, 2022 at 11:08:02AM +0200, Frank Wunderlich wrote:
> > > On Sat, Apr 16, 2022 at 03:54:56PM +0200, Frank Wunderlich wrote:
> > > > From: Frank Wunderlich <[email protected]>
> > > >
> > > > PCIe Lanes can be split to 2 slots with bifurcation.
> > > > Add support for this in existing pcie driver.
>
> > > Is the "rockchip,bifurcation" DT property something that should be
> > > generalized so it's not rockchip-specific? Other controllers are
> > > likely to support similar functionality.
> >
> > I do not know if other controllers support similar functionality,
> > but i ack a property without vendor prefix is better. Should i use
> > "bifurcation" as name or do you think about a different name which
> > is more generic?
>
> Really a question for Rob about what name would be good and where it
> should go.
It might be good to define this as a lane map.
In the Rockchip implementation it's only 2+0 or 1+1, but that isn't
guaranteed if this is made into a standard definition.
So perhaps:
pcie-bifurcation-map = <0>, <1>;
pcie-bifurcation-map = <1>;
pcie-bifurcation-map = <4>, <5>, <6>, <7>;
> Gesendet: Montag, 18. April 2022 um 18:17 Uhr
> Von: "Peter Geis" <[email protected]>
> > On Sun, Apr 17, 2022 at 11:08:02AM +0200, Frank Wunderlich wrote:
> > > > On Sat, Apr 16, 2022 at 03:54:56PM +0200, Frank Wunderlich wrote:
> > > > > From: Frank Wunderlich <[email protected]>
> > > > >
> > > > > PCIe Lanes can be split to 2 slots with bifurcation.
> > > > > Add support for this in existing pcie driver.
> >
> > > > Is the "rockchip,bifurcation" DT property something that should be
> > > > generalized so it's not rockchip-specific? Other controllers are
> > > > likely to support similar functionality.
> > >
> > > I do not know if other controllers support similar functionality,
> > > but i ack a property without vendor prefix is better. Should i use
> > > "bifurcation" as name or do you think about a different name which
> > > is more generic?
> >
> > Really a question for Rob about what name would be good and where it
> > should go.
>
> It might be good to define this as a lane map.
> In the Rockchip implementation it's only 2+0 or 1+1, but that isn't
> guaranteed if this is made into a standard definition.
> So perhaps:
> pcie-bifurcation-map = <0>, <1>;
> pcie-bifurcation-map = <1>;
> pcie-bifurcation-map = <4>, <5>, <6>, <7>;
how about a lane-map like this (from controllers point of view):
rockchip with only 2 lanes (like rk3568):
controller 1:
lane-map = <1 0>;
controller 2:
lane-map = <0 1>;
here bifurcation is set if a controller does not aquire all lanes.Afaik rk3568 cannot select specific lanes so i end up with bifurcation = true/false (an aggregation-mode on phy) again. but it makes dts-property more usable for other devices/SoC.
this contains the maximum of lanes and as mask the lanes to take by the current controller. It is scalable to support more pcie-lanes (x2 x4 x8)
example for 2 controllers with PCIe x4 (with 8 lanes available):
lane-map=<0 0 0 0 1 1 1 1>;
lane-map=<1 1 1 1 0 0 0 0>;
of course they can be mixed, if driver supports this.
lane-map=<0 1 0 1 0 1 0 1>;
lane-map=<1 0 1 0 1 0 1 0>;
such lane-map is more flexible
regards Frank