PCI: Avoid building empty drivers

There are harmless warnings when compile testing the kernel with
CONFIG_TRIM_UNUSED_KSYMS:

  drivers/pci/controller/dwc/pcie-al.o: no symbols
  drivers/pci/controller/pci-thunder-ecam.o: no symbols
  drivers/pci/controller/pci-thunder-pem.o: no symbols

The problem here is that the host drivers get built even when the
configuration symbols are all disabled, as they pretend to not be drivers
but are silently enabled because of the promise that ACPI-based systems
need no drivers.

Add back the normal symbols to have these drivers built, and change the
logic to otherwise only build them when both CONFIG_PCI_QUIRKS and
CONFIG_ACPI are enabled.

As a side-effect, this enables compile-testing the drivers on other
architectures, which in turn needs the acpi_get_rc_resources() function to
be defined.

Link: https://lore.kernel.org/r/20210308152501.2135937-3-arnd@kernel.orgSigned-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NRobert Richter <rric@kernel.org>

drivers/pci/controller/Makefile

@@ -11,10 +11,13 @@ obj-$(CONFIG_PCIE_RCAR_HOST) += pcie-rcar.o pcie-rcar-host.o
 obj-$(CONFIG_PCIE_RCAR_EP) += pcie-rcar.o pcie-rcar-ep.o
 obj-$(CONFIG_PCI_HOST_COMMON) += pci-host-common.o
 obj-$(CONFIG_PCI_HOST_GENERIC) += pci-host-generic.o
+obj-$(CONFIG_PCI_HOST_THUNDER_ECAM) += pci-thunder-ecam.o
+obj-$(CONFIG_PCI_HOST_THUNDER_PEM) += pci-thunder-pem.o
 obj-$(CONFIG_PCIE_XILINX) += pcie-xilinx.o
 obj-$(CONFIG_PCIE_XILINX_NWL) += pcie-xilinx-nwl.o
 obj-$(CONFIG_PCIE_XILINX_CPM) += pcie-xilinx-cpm.o
 obj-$(CONFIG_PCI_V3_SEMI) += pci-v3-semi.o
+obj-$(CONFIG_PCI_XGENE) += pci-xgene.o
 obj-$(CONFIG_PCI_XGENE_MSI) += pci-xgene-msi.o
 obj-$(CONFIG_PCI_VERSATILE) += pci-versatile.o
 obj-$(CONFIG_PCIE_IPROC) += pcie-iproc.o
@@ -47,8 +50,10 @@ obj-y				+= mobiveil/
 # ARM64 and use internal ifdefs to only build the pieces we need
 # depending on whether ACPI, the DT driver, or both are enabled.
 
-ifdef CONFIG_PCI
+ifdef CONFIG_ACPI
+ifdef CONFIG_PCI_QUIRKS
 obj-$(CONFIG_ARM64) += pci-thunder-ecam.o
 obj-$(CONFIG_ARM64) += pci-thunder-pem.o
 obj-$(CONFIG_ARM64) += pci-xgene.o
 endif
+endif

drivers/pci/controller/dwc/Makefile

@@ -31,7 +31,12 @@ obj-$(CONFIG_PCIE_UNIPHIER_EP) += pcie-uniphier-ep.o
 # ARM64 and use internal ifdefs to only build the pieces we need
 # depending on whether ACPI, the DT driver, or both are enabled.
 
-ifdef CONFIG_PCI
+obj-$(CONFIG_PCIE_AL) += pcie-al.o
+obj-$(CONFIG_PCI_HISI) += pcie-hisi.o
+
+ifdef CONFIG_ACPI
+ifdef CONFIG_PCI_QUIRKS
 obj-$(CONFIG_ARM64) += pcie-al.o
 obj-$(CONFIG_ARM64) += pcie-hisi.o
 endif
+endif