The ASPEED AST2600 has 2 Virtual UARTs accessible over PCI.
The ASPEED AST2600 can be used as a PCI device.
2 Virtual UART can be exposed to the host via this PCI device.
These are 8250-compatible register sets and can be used to have UART
communication between the PCI BMC and the host.
This boolean can be set to specify if a VUART is used over PCI. A VUART
over PCI needs a syscon phandle. The syscon gives a regmap to the SCU,
which is used to set the enable bits of the PCI device.
On the aspeed's chips, the clocks phandle already points at the SCU node.
But deriving the regmap from the clock provider would misuse the clocks
binding. An explicit syscon phandle states the dependency directly.
Signed-off-by: Grégoire Layet <gregoire.layet@9elements.com>
---
.../devicetree/bindings/serial/8250.yaml | 22 +++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/Documentation/devicetree/bindings/serial/8250.yaml b/Documentation/devicetree/bindings/serial/8250.yaml
index 8f22121381fc..2ea8981bba80 100644
--- a/Documentation/devicetree/bindings/serial/8250.yaml
+++ b/Documentation/devicetree/bindings/serial/8250.yaml
@@ -27,6 +27,16 @@ allOf:
enum:
- aspeed,ast2500-vuart
- aspeed,ast2600-vuart
+ - if:
+ required:
+ - aspeed,vuart-over-pci
+ then:
+ required:
+ - syscon
+ properties:
+ compatible:
+ contains:
+ const: aspeed,ast2600-vuart
- if:
properties:
compatible:
@@ -223,6 +233,12 @@ properties:
- const: uartclk
- const: reg
+ syscon:
+ $ref: /schemas/types.yaml#/definitions/phandle
+ description:
+ Phandle to the SCU syscon, used to enable the VUART over the BMC PCI
+ device. Only applicable to aspeed,ast2600-vuart.
+
dmas:
minItems: 1
maxItems: 4
@@ -316,6 +332,12 @@ properties:
polarity (IRQ_TYPE_LEVEL_LOW or IRQ_TYPE_LEVEL_HIGH). Only
applicable to aspeed,ast2500-vuart and aspeed,ast2600-vuart.
+ aspeed,vuart-over-pci:
+ type: boolean
+ description:
+ Enable the VUART over the BMC PCI device. Only applicable to
+ aspeed,ast2600-vuart.
+
required:
- reg
- interrupts
--
2.54.0
On Wed, Jul 08, 2026 at 03:35:54PM +0000, Grégoire Layet wrote: > The ASPEED AST2600 has 2 Virtual UARTs accessible over PCI. > The ASPEED AST2600 can be used as a PCI device. > 2 Virtual UART can be exposed to the host via this PCI device. > These are 8250-compatible register sets and can be used to have UART > communication between the PCI BMC and the host. > > This boolean can be set to specify if a VUART is used over PCI. A VUART > over PCI needs a syscon phandle. The syscon gives a regmap to the SCU, > which is used to set the enable bits of the PCI device. > On the aspeed's chips, the clocks phandle already points at the SCU node. > But deriving the regmap from the clock provider would misuse the clocks > binding. An explicit syscon phandle states the dependency directly. > > Signed-off-by: Grégoire Layet <gregoire.layet@9elements.com> > --- > .../devicetree/bindings/serial/8250.yaml | 22 +++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/Documentation/devicetree/bindings/serial/8250.yaml b/Documentation/devicetree/bindings/serial/8250.yaml > index 8f22121381fc..2ea8981bba80 100644 > --- a/Documentation/devicetree/bindings/serial/8250.yaml > +++ b/Documentation/devicetree/bindings/serial/8250.yaml > @@ -27,6 +27,16 @@ allOf: > enum: > - aspeed,ast2500-vuart > - aspeed,ast2600-vuart > + - if: > + required: > + - aspeed,vuart-over-pci > + then: > + required: > + - syscon > + properties: > + compatible: > + contains: > + const: aspeed,ast2600-vuart else: ... disallow new properties (see example-schema) > - if: > properties: > compatible: > @@ -223,6 +233,12 @@ properties: > - const: uartclk > - const: reg > > + syscon: That's explicitly forbidden by writing bindings (and mentioned as the antipattern in my older talks about DT). > + $ref: /schemas/types.yaml#/definitions/phandle > + description: > + Phandle to the SCU syscon, used to enable the VUART over the BMC PCI > + device. Only applicable to aspeed,ast2600-vuart. > + > dmas: > minItems: 1 > maxItems: 4 > @@ -316,6 +332,12 @@ properties: > polarity (IRQ_TYPE_LEVEL_LOW or IRQ_TYPE_LEVEL_HIGH). Only > applicable to aspeed,ast2500-vuart and aspeed,ast2600-vuart. > > + aspeed,vuart-over-pci: > + type: boolean > + description: > + Enable the VUART over the BMC PCI device. Only applicable to > + aspeed,ast2600-vuart. > + > required: > - reg > - interrupts > -- > 2.54.0 >
Hi Krzysztof. On Thu, 9 Jul 2026 at 10:54, Krzysztof Kozlowski <krzk@kernel.org> wrote: > > ... > > @@ -27,6 +27,16 @@ allOf: > > enum: > > - aspeed,ast2500-vuart > > - aspeed,ast2600-vuart > > + - if: > > + required: > > + - aspeed,vuart-over-pci > > + then: > > + required: > > + - syscon > > + properties: > > + compatible: > > + contains: > > + const: aspeed,ast2600-vuart > > else: > ... > disallow new properties (see example-schema) Yes it was missing. Acknowledged. > > > - if: > > properties: > > compatible: > > @@ -223,6 +233,12 @@ properties: > > - const: uartclk > > - const: reg > > > > + syscon: > > That's explicitly forbidden by writing bindings (and mentioned as the > antipattern in my older talks about DT). Missed that. Should it be named to 'aspeed,scu-syscon' as the aspeed SCU is used for all the peripherals. Or should it be named to 'aspeed,pci-syscon' to specify its purpose in this context. From what I have gathered, current convention would use the specific name 'aspeed,pci-syscon'. Would like some feedback on this! > > + $ref: /schemas/types.yaml#/definitions/phandle > > + description: > > + Phandle to the SCU syscon, used to enable the VUART over the BMC PCI > > + device. Only applicable to aspeed,ast2600-vuart. > > + > > ... Thanks Regards, Grégoire
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