On Tue, Jun 08, 2021 at 09:11:27PM +0100, Jon Hunter wrote:
> On 08/06/2021 19:34, Vidya Sagar wrote:
>
> ...
>
> >>> What is the purpose of PCIE_TEGRA194_EP (added by c57247f940e8 ("PCI:
> >>> tegra: Add support for PCIe endpoint mode in Tegra194") [1])? I don't
> >>> see any reference to it in a makefile or a source file.
> >>>
> >>> It looks like one can build a single driver that works in either host
> >>> or endpoint mode, depending on whether a DT node matches
> >>> "nvidia,tegra194-pcie" or "nvidia,tegra194-pcie-ep".
> >>>
> >>> So I think PCIE_TEGRA194_EP is superfluous and should be removed and
> >>> you should have a single tristate Kconfig option.
> >>
> >> This is a good point.
> >>
> >> Sagar, any reason for this?
> > Although it is the same driver that works for both HOST mode and EP
> > mode, PCIE_TEGRA194_EP depends on PCI_ENDPOINT whereas the
> > PCIE_TEGRA194_HOST mode doesn't. Similarly the PCIE_TEGRA194_HOST mode
> > depends on PCI_MSI_IRQ_DOMAIN which PCIE_TEGRA194_EP doesn't depend on.
> > It is possible to have end point mode support disabled (at sub-system
> > level) in the system yet pcie-tegra194 can be compiled for the host mode
> > vice-a-versa for the endpoint mode.
> > Hence, appropriate config HOST/EP needs to be selected to make sure that
> > the rest of the dependencies are enabled in the system.
> > Hope I'm able to give the rationale correctly here.
>
> Yes but should we combine them like this ...
>
> diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
> index 423d35872ce4..206455a9b70d 100644
> --- a/drivers/pci/controller/dwc/Kconfig
> +++ b/drivers/pci/controller/dwc/Kconfig
> @@ -254,15 +254,12 @@ config PCI_MESON
> implement the driver.
>
> config PCIE_TEGRA194
> - tristate
> -
> -config PCIE_TEGRA194_HOST
> - tristate "NVIDIA Tegra194 (and later) PCIe controller - Host Mode"
> + tristate "NVIDIA Tegra194 (and later) PCIe controller"
> depends on ARCH_TEGRA_194_SOC || COMPILE_TEST
> - depends on PCI_MSI_IRQ_DOMAIN
> - select PCIE_DW_HOST
> + depends on PCI_MSI_IRQ_DOMAIN || PCI_ENDPOINT
> + select PCIE_DW_HOST if PCI_MSI_IRQ_DOMAIN
> + select PCIE_DW_EP if PCI_ENDPOINT
> select PHY_TEGRA194_P2U
> - select PCIE_TEGRA194
> help
> Enables support for the PCIe controller in the NVIDIA Tegra194 SoC to
> work in host mode. There are two instances of PCIe controllers in
> @@ -271,21 +268,6 @@ config PCIE_TEGRA194_HOST
> in order to enable device-specific features PCIE_TEGRA194_EP must be
> selected. This uses the DesignWare core.
>
> -config PCIE_TEGRA194_EP
> - tristate "NVIDIA Tegra194 (and later) PCIe controller - Endpoint Mode"
> - depends on ARCH_TEGRA_194_SOC || COMPILE_TEST
> - depends on PCI_ENDPOINT
> - select PCIE_DW_EP
> - select PHY_TEGRA194_P2U
> - select PCIE_TEGRA194
> - help
> - Enables support for the PCIe controller in the NVIDIA Tegra194 SoC to
> - work in endpoint mode. There are two instances of PCIe controllers in
> - Tegra194. This controller can work either as EP or RC. In order to
> - enable host-specific features PCIE_TEGRA194_HOST must be selected and
> - in order to enable device-specific features PCIE_TEGRA194_EP must be
> - selected. This uses the DesignWare core.
I'm not a Kconfig expert, but I really like that solution, as long as
it addresses Vidya's concerns about RP/EP dependencies.
Looks like the Kconfig help text should be updated to remove the
other PCIE_TEGRA194_EP reference? Maybe it should include a clue
about how the connections to host/endpoint support, e.g., "includes
endpoint support if PCI_ENDPOINT is enabled"?
> Furthermore, I wonder if we should just move the code
> that is required for ACPI into it's own file like
> drivers/pci/controller/dwc/pcie-tegra194-acpi.c?
That might simplify things. I think the reason we started with things
in one file is because for some drivers there's a lot of shared stuff
(#defines, register accessors) between the quirk and the native host
driver. Either you have to put it all in one file, or you have to add
a shared .h file and make some of that stuff non-static.
Bjorn
