Re: [PATCH V13 08/12] dt-bindings: Add PCIe supports-clkreq property

[Vidya Sagar]

On 7/10/2019 8:58 PM, Lorenzo Pieralisi wrote:
> On Wed, Jul 10, 2019 at 11:52:08AM +0530, Vidya Sagar wrote:
> > Some host controllers need to know the existence of clkreq signal routing to
> > downstream devices to be able to advertise low power features like ASPM L1
> > substates. Without clkreq signal routing being present, enabling ASPM L1 sub
> > states might lead to downstream devices falling off the bus. Hence a new device
>
> You mean "being disconnected from the bus" right ? I will update it.
Yes. I meant the same.

> Lorenzo
>
> > tree property 'supports-clkreq' is added to make such host controllers
> > aware of clkreq signal routing to downstream devices.
> >
> > Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> > Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
> > Reviewed-by: Thierry Reding <treding@xxxxxxxxxx>
> > ---
> > V13:
> > * None
> >
> > V12:
> > * Rebased on top of linux-next top of the tree
> >
> > V11:
> > * None
> >
> > V10:
> > * None
> >
> > V9:
> > * None
> >
> > V8:
> > * None
> >
> > V7:
> > * None
> >
> > V6:
> > * s/Documentation\/devicetree/dt-bindings/ in the subject
> >
> > V5:
> > * None
> >
> > V4:
> > * Rebased on top of linux-next top of the tree
> >
> > V3:
> > * None
> >
> > V2:
> > * This is a new patch in v2 series
> >
> >   Documentation/devicetree/bindings/pci/pci.txt | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/pci/pci.txt b/Documentation/devicetree/bindings/pci/pci.txt
> > index 2a5d91024059..29bcbd88f457 100644
> > --- a/Documentation/devicetree/bindings/pci/pci.txt
> > +++ b/Documentation/devicetree/bindings/pci/pci.txt
> > @@ -27,6 +27,11 @@ driver implementation may support the following properties:
> >   - reset-gpios:
> >      If present this property specifies PERST# GPIO. Host drivers can parse the
> >      GPIO and apply fundamental reset to endpoints.
> > +- supports-clkreq:
> > +   If present this property specifies that CLKREQ signal routing exists from
> > +   root port to downstream device and host bridge drivers can do programming
> > +   which depends on CLKREQ signal existence. For example, programming root port
> > +   not to advertise ASPM L1 Sub-States support if there is no CLKREQ signal.
> >   
> >   PCI-PCI Bridge properties
> >   -------------------------
> > --
> > 2.17.1