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

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Date:   Wed, 10 Jul 2019 22:44:20 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:     <bhelgaas@...gle.com>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <kishon@...com>, <catalin.marinas@....com>,
        <will.deacon@....com>, <jingoohan1@...il.com>,
        <gustavo.pimentel@...opsys.com>, <digetx@...il.com>,
        <mperttunen@...dia.com>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <kthota@...dia.com>,
        <mmaddireddy@...dia.com>, <sagar.tv@...il.com>
Subject: Re: [PATCH V13 08/12] dt-bindings: Add PCIe supports-clkreq property

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