On 6/8/2021 6:50 PM, Jon Hunter wrote:
On 08/06/2021 14:02, Bjorn Helgaas wrote:
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.
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.
- Vidya Sagar
Jon
--
nvpublic
