Re: [PATCH RFC v4 9/9] arm64: dts: qcom: glymur: Wire PCIe3a/3b to shared Gen5x8 PHY

[Qiang Yu <qiang.yu@oss.qualcomm.com>]

On Mon, Jun 29, 2026 at 11:20:07AM +0200, Konrad Dybcio wrote:
> On 6/29/26 7:05 AM, Qiang Yu wrote:
> > On Wed, Jun 17, 2026 at 01:19:49PM +0200, Konrad Dybcio wrote:
> >> On 5/19/26 7:47 AM, Qiang Yu wrote:
> >>> Glymur PCIe3 uses a single shared Gen5x8 QMP PHY block. Model PCIe3a and
> >>> PCIe3b as consumers of that shared PHY provider instead of separate PHY
> >>> nodes.
> >>>
> >>> Update the DTS wiring to:
> >>> - point GCC PCIe3A/3B pipe parents to the shared PHY clock outputs
> >>> - add PCIe3a controller node and route PCIe3a/PCIe3b port phys to
> >>>   &pcie3_phy using two-cell PHY arguments
> >>> - configure the shared PHY node with link-mode and dual pipe outputs
> >>>
> >>> Use QMP_PCIE_GLYMUR_MODE_* dt-binding macros for mode selection.
> >>>
> >>> Signed-off-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
> >>> ---
> >>
> >> [...]
> >>
> >>> +		pcie3a: pci@1c10000 {
> >>> +			device_type = "pci";
> >>> +			compatible = "qcom,glymur-pcie", "qcom,pcie-x1e80100";
> >>> +			reg = <0x0 0x01c10000 0x0 0x3000>,
> >>> +			      <0x0 0x70000000 0x0 0xf20>,
> >>> +			      <0x0 0x70000f40 0x0 0xa8>,
> >>> +			      <0x0 0x70001000 0x0 0x4000>,
> >>> +			      <0x0 0x70100000 0x0 0x100000>,
> >>> +			      <0x0 0x01c13000 0x0 0x1000>;
> >>> +			reg-names = "parf",
> >>> +				    "dbi",
> >>> +				    "elbi",
> >>> +				    "atu",
> >>> +				    "config",
> >>> +				    "mhi";
> >>> +			#address-cells = <3>;
> >>> +			#size-cells = <2>;
> >>> +			ranges = <0x01000000 0x0 0x00000000 0x0 0x70200000 0x0 0x100000>,
> >>> +				 <0x02000000 0x0 0x70000000 0x0 0x70300000 0x0 0x3d00000>,
> >>> +				 <0x03000000 0x7 0x00000000 0x7 0x00000000 0x0 0x40000000>,
> >>> +				 <0x43000000 0x70 0x00000000 0x70 0x00000000 0x10 0x00000000>;
> >>> +
> >>> +			bus-range = <0 0xff>;
> >>> +
> >>> +			dma-coherent;
> >>> +
> >>> +			linux,pci-domain = <3>;
> >>> +			num-lanes = <8>;
> >>
> >> Is it fine to keep num-lanes 8 here even for configurations with
> >> bifurcated PHY?
> >>
> >> I would assume so, given essentially this is a x8 host, whose 4
> >> lanes may simply be effectively NC 
> >>
> > Actually, on existing platforms, the PCIe3a and PCIe3b controllers are
> > never enabled at the same time. When PCIe3a is exposed, it is always in an
> > x8 slot. But if we have a x4+x4 platform in future, we can simply override
> > num-lanes to 4 in the board.dts.
> 
> My question is whether that will be necessary - if yes, sure, we
> can do it, but if not, we can conclude on this early and not have
> to fight over it in a couple months
>
I think we do need to override it in that case. If both PCIe3a and PCIe3b
are enabled in x4+x4 mode but PCIe3a keeps num-lanes = <8>, userspace
will see an 8-lane slot. If an x8-capable EP is connected to that slot,
both ends will advertise x8 support, but the link is up at x4. That looks
like a genuine bug from the user's point of view.

- Qiang Yu