On Tue, Jun 08, 2021 at 08:44:49AM +0100, Jon Hunter wrote:
> On 08/06/2021 00:50, Bjorn Helgaas wrote:
>
> ...
>
> > My understanding is that we want pcie-tegra194.c to be:
> >
> > - Built into the kernel when CONFIG_PCIE_TEGRA194=m or =y and
> > CONFIG_ACPI=y and CONFIG_PCI_QUIRKS=y. If we're using the ACPI
> > pci_root.c driver, we must have the MCFG quirk built-in, and this
> > case worked as I expected (this is on x86):
> >
> > $ grep -E "CONFIG_(ACPI\>|PCI_QUIRKS|PCIE_TEGRA194)" .config
> > CONFIG_ACPI=y
> > CONFIG_PCI_QUIRKS=y
> > CONFIG_PCIE_TEGRA194=y
> > CONFIG_PCIE_TEGRA194_HOST=m
> > CONFIG_PCIE_TEGRA194_EP=y
> >
> > $ rm drivers/pci/controller/dwc/pcie-tegra194.*o
> > $ make drivers/pci/controller/dwc/
> > ...
> > CC drivers/pci/controller/dwc/pcie-tegra194.o
> > AR drivers/pci/controller/dwc/built-in.a
> >
> > - Built as a module when CONFIG_PCIE_TEGRA194=m and CONFIG_ACPI is
> > not set. In this case, we're not using the ACPI pci_root.c
> > driver, and we don't need the MCFG quirk built-in, so it should be
> > OK to build a module, and IIUC this patch is supposed to *allow*
> > that. But in my testing, it did *not* build a module. Am I
> > missing something?
> >
> > $ grep -E "CONFIG_(ACPI\>|PCI_QUIRKS|PCIE_TEGRA194)" .config
> > # CONFIG_ACPI is not set
> > # CONFIG_PCI_QUIRKS is not set
> > CONFIG_PCIE_TEGRA194=y
> > CONFIG_PCIE_TEGRA194_HOST=m
> > CONFIG_PCIE_TEGRA194_EP=y
>
> The problem appears to be that you still have CONFIG_PCIE_TEGRA194=y and
> CONFIG_PCIE_TEGRA194_EP=y above. If I have ...
Huh. I can't set CONFIG_PCIE_TEGRA194 directly; it's only selectable
by PCIE_TEGRA194_HOST and PCIE_TEGRA194_EP. PCIE_TEGRA194 is
tristate, but apparently kconfig sets it to the most restrictive,
which I guess makes sense.
So I would expect the shared infrastructure to be built-in if either
driver is built-in, but it's somewhat confusing that
CONFIG_PCIE_TEGRA194_HOST=m results in a builtin driver. If I can set
CONFIG_PCIE_TEGRA194_HOST and CONFIG_PCIE_TEGRA194_EP independently,
it seems like they should *be* independent.
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.
Tangentially related, this cast in tegra_pcie_dw_probe() looks
unnecessary:
pcie->mode = (enum dw_pcie_device_mode)data->mode;
Looks like it was copied from similar code in dra7xx_pcie_probe(),
artpec6_pcie_probe(), and dw_plat_pcie_probe(), which are all littered
with similar unnecessary casts. But that should be solved separately
from the Kconfig question.
[1] https://git.kernel.org/linus/c57247f940e8
> $ grep -E "CONFIG_(ACPI\>|PCI_QUIRKS|PCIE_TEGRA194)" .config
> # CONFIG_ACPI is not set
> CONFIG_PCI_QUIRKS=y
> CONFIG_PCIE_TEGRA194=m
> CONFIG_PCIE_TEGRA194_HOST=m
> # CONFIG_PCIE_TEGRA194_EP is not set
>
>
> >
> > $ rm drivers/pci/controller/dwc/pcie-tegra194.*o
> > $ make drivers/pci/controller/dwc/
> > ...
> > CC drivers/pci/controller/dwc/pcie-tegra194.o
> > AR drivers/pci/controller/dwc/built-in.a
>
> Then I see ...
>
> $ rm drivers/pci/controller/dwc/pcie-tegra194.*o
> $ make drivers/pci/controller/dwc/
> ...
> CC [M] drivers/pci/controller/dwc/pcie-tegra194.o
>
> Cheers
> Jon
>
> --
> nvpublic
