[V7,08/15] dt-bindings: Add PCIe supports-clkreq property
diff mbox series

Message ID 20190517123846.3708-9-vidyas@nvidia.com
State Not Applicable
Headers show
Series
  • Add Tegra194 PCIe support
Related show

Commit Message

Vidya Sagar May 17, 2019, 12:38 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>
---
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(+)

Comments

Thierry Reding May 21, 2019, 10:39 a.m. UTC | #1
On Fri, May 17, 2019 at 06:08:39PM +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
> 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>
> ---
> 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(+)

Reviewed-by: Thierry Reding <treding@nvidia.com>

Patch
diff mbox series

diff --git a/Documentation/devicetree/bindings/pci/pci.txt b/Documentation/devicetree/bindings/pci/pci.txt
index 92c01db610df..d132f9efeb3e 100644
--- a/Documentation/devicetree/bindings/pci/pci.txt
+++ b/Documentation/devicetree/bindings/pci/pci.txt
@@ -24,6 +24,11 @@  driver implementation may support the following properties:
    unsupported link speed, for instance, trying to do training for
    unsupported link speed, etc.  Must be '4' for gen4, '3' for gen3, '2'
    for gen2, and '1' for gen1. Any other values are invalid.
+- 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
 -------------------------