linux-kernel - Re: [PATCH] schemas: pci: Document PCIe T_POWER

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Message-ID: <511ebf46-63ed-45af-9d66-ccd1d944763a@oss.qualcomm.com>
Date: Mon, 10 Nov 2025 18:43:34 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: andersson@...nel.org, robh@...nel.org, manivannan.sadhasivam@...aro.org,
        krzk@...nel.org, helgaas@...nel.org
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        lpieralisi@...nel.org, kw@...ux.com, conor+dt@...nel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree-spec@...r.kernel.org, quic_vbadigan@...cinc.com
Subject: Re: [PATCH] schemas: pci: Document PCIe T_POWER_ON

Please ignore this patch, it has some mistakes which I have sent 
accidentally.

- Krishna Chaitanya.

On 11/10/2025 4:55 PM, Krishna Chaitanya Chundru wrote:
>  From PCIe r6, sec 5.5.4 & Table 5-11 in sec 5.5.5 T_POWER_ON is the
> minimum amount of time(in us) that each component must wait in L1.2.Exit
> after sampling CLKREQ# asserted before actively driving the interface to
> ensure no device is ever actively driving into an unpowered component and
> these values are based on the components and AC coupling capacitors used
> in the connection linking the two components.
>
> This property should be used to indicate the T_POWER_ON for each Root Port.
>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> ---
> Changes in V1:
> - Updated the commit text (Mani).
>
>   dtschema/schemas/pci/pci-bus-common.yaml | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/dtschema/schemas/pci/pci-bus-common.yaml b/dtschema/schemas/pci/pci-bus-common.yaml
> index 5257339..bbe5510 100644
> --- a/dtschema/schemas/pci/pci-bus-common.yaml
> +++ b/dtschema/schemas/pci/pci-bus-common.yaml
> @@ -152,6 +152,15 @@ properties:
>         This property is invalid in host bridge nodes.
>       maxItems: 1
>   
> +  t-power-on-us:
> +    description:
> +      The minimum amount of time that each component must wait in
> +      L1.2.Exit after sampling CLKREQ# asserted before actively driving
> +      the interface to ensure no device is ever actively driving into an
> +      unpowered component. This value is based on the components and AC
> +      coupling capacitors used in the connection linking the two
> +      components(PCIe r6.0, sec 5.5.4).
> +
>     supports-clkreq:
>       description:
>         If present this property specifies that CLKREQ signal routing exists from