linux-kernel - [PATCH V1] schemas: pci: bridge: Document PCI L0s & L1 entry delay and nfts

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Message-Id: <20250106093304.604829-1-krishna.chundru@oss.qualcomm.com>
Date: Mon,  6 Jan 2025 15:03:04 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: andersson@...nel.org, robh@...nel.org, dmitry.baryshkov@...aro.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 Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Subject: [PATCH V1] schemas: pci: bridge: Document PCI L0s & L1 entry delay and nfts

Some controllers and endpoints provide provision to program the entry
delays of L0s & L1 which will allow the link to enter L0s & L1 more
aggressively to save power.

As per PCIe spec 6 sec 4.2.5.6, the number of Fast Training Sequence (FTS)
can be programmed by the controllers or endpoints that is used for bit and
Symbol lock when transitioning from L0s to L0 based upon the PCIe data rate
FTS value can vary. So define a array for each data rate for nfts.

These values needs to be programmed before link training.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
---
- This change was suggested in this patch: https://lore.kernel.org/all/20241211060000.3vn3iumouggjcbva@thinkpad/
---
 dtschema/schemas/pci/pci-bus-common.yaml | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/dtschema/schemas/pci/pci-bus-common.yaml b/dtschema/schemas/pci/pci-bus-common.yaml
index 94b648f..f0655ba 100644
--- a/dtschema/schemas/pci/pci-bus-common.yaml
+++ b/dtschema/schemas/pci/pci-bus-common.yaml
@@ -128,6 +128,16 @@ properties:
     $ref: /schemas/types.yaml#/definitions/uint32
     enum: [ 1, 2, 4, 8, 16, 32 ]
 
+  nfts:
+    description:
+      Number of Fast Training Sequence (FTS) used during L0s to L0 exit for bit
+      and Symbol lock.
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    minItems: 1
+    maxItems: 5
+    items:
+      maximum: 255
+
   reset-gpios:
     description: GPIO controlled connection to PERST# signal
     maxItems: 1
@@ -150,6 +160,12 @@ properties:
     description: Disables ASPM L0s capability
     type: boolean
 
+  aspm-l0s-entry-delay-ns:
+    description: Aspm l0s entry delay.
+
+  aspm-l1-entry-delay-ns:
+    description: Aspm l1 entry delay.
+
   vpcie12v-supply:
     description: 12v regulator phandle for the slot
 
-- 
2.34.1