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. 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 >
