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[V12,08/12] dt-bindings: Add PCIe supports-clkreq property

Message ID 20190701124010.7484-9-vidyas@nvidia.com (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show
Series Add Tegra194 PCIe support | expand

Commit Message

Vidya Sagar July 1, 2019, 12:40 p.m. UTC 
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
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@nvidia.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Thierry Reding <treding@nvidia.com>
---
Changes since [v11]:
* Rebased on top of linux-next top of the tree

Changes since [v10]:
* None

Changes since [v9]:
* None

Changes since [v8]:
* None

Changes since [v7]:
* None

Changes since [v6]:
* None

Changes since [v5]:
* s/Documentation\/devicetree/dt-bindings/ in the subject

Changes since [v4]:
* None

Changes since [v3]:
* Rebased on top of linux-next top of the tree

Changes since [v2]:
* None

Changes since [v1]:
* This is a new patch in v2 series

 Documentation/devicetree/bindings/pci/pci.txt | 5 +++++
 1 file changed, 5 insertions(+)
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Patch

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
 -------------------------