Re: [PATCH v3 1/5] dt-bindings: phy: qcom,sc8280xp-qmp-pcie-phy: Add support for glymur Gen5 x8 bifurcation mode

[Qiang Yu]

On Wed, Apr 15, 2026 at 09:50:28AM +0200, Krzysztof Kozlowski wrote:
> On Sun, Apr 12, 2026 at 11:25:56PM -0700, Qiang Yu wrote:
> > The Glymur SoC has pcie3a and pcie3b PHYs that can operate in two modes:
> > 
> > 1. Independent 4-lane mode: Each PHY operates as a separate PCIe Gen5
> >    4-lane interface, compatible with qcom,glymur-qmp-gen5x4-pcie-phy
> > 2. Bifurcation mode (8-lane): pcie3a phy acts as leader and pcie3b phy as
> >    follower to form a single 8-lane PCIe Gen5 interface
> > 
> > In bifurcation mode, the hardware design requires controlling additional
> > resources beyond the standard pcie3a PHY configuration:
> > 
> > - pcie3b's aux_clk (phy_b_aux)
> > - pcie3b's phy_gdsc power domain
> > - pcie3b's bcr/nocsr reset
> > 
> > Add qcom,glymur-qmp-gen5x8-pcie-phy compatible string to document this
> > 8-lane bifurcation configuration.
> 
> Do you describe PCI3A or PCI3B or something combined PCI3?

I describe a single x8 PHY with resources from both the pcie3a and pcie3b
PHY blocks for x8 operation.

> 
> > 
> > The phy_b_aux clock is used as the 6th clock instead of pipediv2,
> > requiring the clock-names enum to be extended to support both
> > [phy_b_aux, pipediv2] options at index 5. This follows the existing
> > pattern used for [rchng, refgen] clocks at index 3.
> > 
> > Signed-off-by: Qiang Yu <qiang.yu@xxxxxxxxxxxxxxxx>
> > ---
> >  .../bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml   | 53 ++++++++++++++++++----
> >  1 file changed, 45 insertions(+), 8 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml
> > index 3a35120a77ec0ceb814a1cdcacff32fef32b4f7b..14eba5d705b1956c1bb00cc8c95171ed6488299b 100644
> > --- a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml
> > +++ b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml
> > @@ -18,6 +18,7 @@ properties:
> >      enum:
> >        - qcom,glymur-qmp-gen4x2-pcie-phy
> >        - qcom,glymur-qmp-gen5x4-pcie-phy
> > +      - qcom,glymur-qmp-gen5x8-pcie-phy
> 
> That's the same device as 5x4, no? One device, one compatible and this
> suggests you will have three PCI phys in the DT - two 5x4 and one 5x8?
> 

It is not the same as the 5x4 PHY. In DT, we model three PHY nodes:
phy_3a (1x4), phy_3b (1x4), and a separate phy_1x8 node for x8 mode.

> 
> >        - qcom,kaanapali-qmp-gen3x2-pcie-phy
> >        - qcom,qcs615-qmp-gen3x1-pcie-phy
> >        - qcom,qcs8300-qmp-gen4x2-pcie-phy
> > @@ -68,20 +69,27 @@ properties:
> >        - const: ref
> >        - enum: [rchng, refgen]
> >        - const: pipe
> > -      - const: pipediv2
> > +      - enum: [phy_b_aux, pipediv2]
> >  
> >    power-domains:
> > -    maxItems: 1
> > +    minItems: 1
> > +    items:
> > +      - description: PCIe PHY power domain. For PHYs supporting
> > +          bifurcation mode, this is the leader PHY power domain.
> > +      - description: Additional PCIe PHY power domain for PHYs supporting
> > +          bifurcation mode, used by the follower PHY.
> >  
> >    resets:
> >      minItems: 1
> > -    maxItems: 2
> > +    maxItems: 4
> >  
> >    reset-names:
> >      minItems: 1
> >      items:
> >        - const: phy
> >        - const: phy_nocsr
> > +      - const: phy_b
> > +      - const: phy_b_nocsr
> 
> And now I doubt that all the changes here are for duplicated node.
>

All the changes here are for 1x8 PHY node.

> Maybe just the commit msg is confusing and instead of describing some
> node which combines two other phys just say what device is here being
> described.
>

Okay, I will focus on describing the required resources. Is the
description below clearer?

Glymur has two physical Gen5x4 PCIe PHY blocks: pcie3a phy and pcie3b phy.

Besides the independent 2x4 topology, Glymur also supports an x8 topology
that is described as a dedicated 1x8 PHY DT node. In this topology, the
x8 PHY uses resources from both PHY blocks: pcie3a (leader) and pcie3b
(follower) resources.

Add qcom,glymur-qmp-gen5x8-pcie-phy to describe this x8 PHY node and
document its extra required resources:
- pcie3b PHY aux clock (phy_b_aux)
- pcie3b PHY power domain
- pcie3b PHY BCR/NOCSR resets

The phy_b_aux clock is used as the 6th clock instead of pipediv2,
requiring the clock-names enum to be extended to support both
[phy_b_aux, pipediv2] options at index 5. This follows the existing
pattern used for [rchng, refgen] clocks at index 3.

- Qiang Yu

> Best regards,
> Krzysztof
>