[PATCH V3 2/2] schemas: pci: bridge: Document PCIe N_FTS

Krishna Chaitanya Chundru
2025-02-16T01:45:46Z

Per PCIe r6.0, sec 4.2.5.1, during Link training, a PCIe component
captures the N_FTS value it receives. Per 4.2.5.6, when
transitioning the Link from L0s to L0, it must transmit N_FTS Fast
Training Sequences to enable the receiver to obtain bit and Symbol
lock.

Components may have device-specific ways to configure N_FTS values
to advertise during Link training. Define an n_fts array with an
entry for each supported data rate.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
dtschema/schemas/pci/pci-bus-common.yaml | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/dtschema/schemas/pci/pci-bus-common.yaml b/dtschema/schemas/pci/pci-bus-common.yaml
index a9309af..ca97a00 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 ]

+ n-fts:
+ description:
+ The number of Fast Training Sequences (N_FTS) required by the
+ Receiver (this component) when transitioning the Link from L0s
+ to L0; advertised during initial Link training. Each entry in
+ the array specifies a PCIe data rate
+ $ref: /schemas/types.yaml#/definitions/uint8-array
+ minItems: 1
+ maxItems: 5
+
reset-gpios:
description: GPIO controlled connection to PERST# signal
maxItems: 1
--
2.34.1