[PATCH] schemas: pci: Document PCIe T_POWER_ON

[PATCH] schemas: pci: Document PCIe T_POWER_ON

[Krishna Chaitanya Chundru]

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@oss.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
-- 
2.34.1

Re: [PATCH] schemas: pci: Document PCIe T_POWER_ON

[Krishna Chaitanya Chundru]

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@oss.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

[PATCH] schemas: pci: Document PCIe T_POWER_ON

[Krishna Chaitanya Chundru]

From PCIe r6, sec 5.5.4 & sec 5.5.5 T POWER_ON is 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 and these values are based on
the components and AC coupling capacitors used in the connection linking
the two components.

Certain controllers may need to program this before enumeration, such
controllers can use this property to program it.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 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
-- 
2.34.1

Re: [PATCH] schemas: pci: Document PCIe T_POWER_ON

[Manivannan Sadhasivam]

On Thu, Nov 06, 2025 at 05:09:51PM +0530, Krishna Chaitanya Chundru wrote:
> From PCIe r6, sec 5.5.4 & sec 5.5.5 T POWER_ON is the minimum amount

T_POWER_ON

You should provide reference to the Table 5-11, where T_POWER_ON is described.

> 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.
> 
> Certain controllers may need to program this before enumeration, such
> controllers can use this property to program it.
> 

I'd remove this statement and just mention that this property should be used to
indicate the T_POWER_ON for each Root Port.

- Mani

-- 
மணிவண்ணன் சதாசிவம்

Re: [PATCH] schemas: pci: Document PCIe T_POWER_ON

[Krishna Chaitanya Chundru]

On 11/6/2025 6:08 PM, Manivannan Sadhasivam wrote:
> On Thu, Nov 06, 2025 at 05:09:51PM +0530, Krishna Chaitanya Chundru wrote:
>>  From PCIe r6, sec 5.5.4 & sec 5.5.5 T POWER_ON is the minimum amount
> T_POWER_ON
>
> You should provide reference to the Table 5-11, where T_POWER_ON is described
Actually 5.5.5 section has only table 5-11 which describes this, I will 
add the Table 5-11
reference also in next patch.
>> 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.
>>
>> Certain controllers may need to program this before enumeration, such
>> controllers can use this property to program it.
>>
> I'd remove this statement and just mention that this property should be used to
> indicate the T_POWER_ON for each Root Port.
ack.

- Krishna Chaitanya.
> - Mani
>