[RFC] ARM: add multi_v7_lpae_defconfig

[Nicolas Saenz Julienne]

The only missing configuration option preventing us from using
multi_v7_defconfig with the RPi4 is ARM_LPAE. It's needed as the PCIe
controller found on the SoC depends on 64bit addressing, yet can't be
included as not all v7 boards support LPAE.

Introduce multi_v7_lpae_defconfig, built off multi_v7_defconfig, which will
avoid us having to duplicate and maintain multiple similar configurations.

Note that merge_into_defconfig was taken from arch/powerpc/Makefile.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
---
 arch/arm/Makefile            | 14 ++++++++++++++
 arch/arm/configs/lpae.config |  1 +
 2 files changed, 15 insertions(+)
 create mode 100644 arch/arm/configs/lpae.config

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index db857d07114f..3d157777a465 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -356,6 +356,20 @@ archclean:
 # My testing targets (bypasses dependencies)
 bp:;	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $(boot)/bootpImage
 
+# Used to create 'merged defconfigs'
+# To use it $(call) it with the first argument as the base defconfig
+# and the second argument as a space separated list of .config files to merge,
+# without the .config suffix.
+define merge_into_defconfig
+	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/kconfig/merge_config.sh \
+		-m -O $(objtree) $(srctree)/arch/$(ARCH)/configs/$(1) \
+		$(foreach config,$(2),$(srctree)/arch/$(ARCH)/configs/$(config).config)
+	+$(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
+endef
+
+PHONY += multi_v7_lpae_defconfig
+multi_v7_lpae_defconfig:
+	$(call merge_into_defconfig,multi_v7_defconfig,lpae)
 
 define archhelp
   echo  '* zImage        - Compressed kernel image (arch/$(ARCH)/boot/zImage)'
diff --git a/arch/arm/configs/lpae.config b/arch/arm/configs/lpae.config
new file mode 100644
index 000000000000..19bab134e014
--- /dev/null
+++ b/arch/arm/configs/lpae.config
@@ -0,0 +1 @@
+CONFIG_ARM_LPAE=y
-- 
2.24.1