linux-kernel - [PATCH v2] schemas: pci: Document PCIe T_POWER

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Message-Id: <20251110112947.2071036-1-krishna.chundru@oss.qualcomm.com>
Date: Mon, 10 Nov 2025 16:59:47 +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,
        krishna.chundru@....qualcomm.com
Subject: [PATCH v2] schemas: pci: Document PCIe T_POWER_ON

>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 commiit text (Mani).
- Link to v1: https://lore.kernel.org/all/20251110112550.2070659-1-krishna.chundru@oss.qualcomm.com/#t

 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