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

[Vidya Sagar <vidyas@nvidia.com>]

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@nvidia.com>
>> Reviewed-by: Rob Herring <robh@kernel.org>
>> Reviewed-by: Thierry Reding <treding@nvidia.com>
>> ---
>> 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
>>