PCIe tegra194 endpoint mode regulator question

PCIe tegra194 endpoint mode regulator question

[Niklas Cassel]

Hello Tegra PCIe maintainers,

Looking at the device tree binding for Tegra PCIe endpoint mode:
Documentation/devicetree/bindings/pci/nvidia,tegra194-pcie-ep.yaml

We can see that 'vddio-pex-ctl-supply' is marked as required.

However, when inspecting the driver itself:
drivers/pci/controller/dwc/pcie-tegra194.c

regulator_enable(pcie->pex_ctl_supply);
is only called in tegra_pcie_config_controller().
tegra_pcie_init_controller() is called by tegra_pcie_config_rp()
(Root Complex mode), however regulator_enable(pcie->pex_ctl_supply);
is never called by tegra_pcie_config_ep() or pex_ep_event_pex_rst_deassert(),
or any other function called when the driver is using any of the
PCIe endpoint mode compatible strings.

So, I think there is something wrong here.

Either:
1) 'vddio-pex-ctl-supply' shouldn't be marked as required in the
   PCIe endpoint mode device tree binding (or perhaps not be there
   at all, since regulator_enable(pcie->pex_ctl_supply) is never called.)

2) drivers/pci/controller/dwc/pcie-tegra194.c should call
   regulator_enable(pcie->pex_ctl_supply) even in the endpoint mode case.


Looking forward to your feedback.


Kind regards,
Niklas

Re: PCIe tegra194 endpoint mode regulator question

[Jon Hunter]

Hi Sagar,

On 17/09/2025 10:26, Niklas Cassel wrote:
> Hello Tegra PCIe maintainers,
> 
> Looking at the device tree binding for Tegra PCIe endpoint mode:
> Documentation/devicetree/bindings/pci/nvidia,tegra194-pcie-ep.yaml
> 
> We can see that 'vddio-pex-ctl-supply' is marked as required.
> 
> However, when inspecting the driver itself:
> drivers/pci/controller/dwc/pcie-tegra194.c
> 
> regulator_enable(pcie->pex_ctl_supply);
> is only called in tegra_pcie_config_controller().
> tegra_pcie_init_controller() is called by tegra_pcie_config_rp()
> (Root Complex mode), however regulator_enable(pcie->pex_ctl_supply);
> is never called by tegra_pcie_config_ep() or pex_ep_event_pex_rst_deassert(),
> or any other function called when the driver is using any of the
> PCIe endpoint mode compatible strings.
> 
> So, I think there is something wrong here.
> 
> Either:
> 1) 'vddio-pex-ctl-supply' shouldn't be marked as required in the
>     PCIe endpoint mode device tree binding (or perhaps not be there
>     at all, since regulator_enable(pcie->pex_ctl_supply) is never called.)
> 
> 2) drivers/pci/controller/dwc/pcie-tegra194.c should call
>     regulator_enable(pcie->pex_ctl_supply) even in the endpoint mode case.


Looks like you added this. Can you confirm if this is needed or not?

Jon

-- 
nvpublic