diff mbox series

[v5,3/7] LoongArch: Allow device trees to be built into the kernel

Message ID 8da27d46fbc72e2e178d81e2f18abec7d9bd725a.1702862778.git.zhoubinbin@loongson.cn
State New
Headers show
Series LoongArch: Add built-in dtb support | expand

Commit Message

Binbin Zhou Dec. 18, 2023, 1:52 a.m. UTC 
During the upstream progress of those DT-based drivers, DT properties
are changed a lot so very different from those in existing bootloaders.
It is inevitably that some existing systems do not provide a standard,
canonical device tree to the kernel at boot time. So let's provide a
device tree table in the kernel, keyed by the dts filename, containing
the relevant DTBs.

We can use the built-in dts files as references. Each SoC has only one
built-in dts file which describes all possible device information of
that SoC, so the dts files are good examples during development.

And as a reference, our built-in dts file only enables the most basic
bootable combinations (so it is generic enough), acts as an alternative
in case the dts in the bootloader is unexpected.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 arch/loongarch/Kconfig           | 18 ++++++++++++++++++
 arch/loongarch/Makefile          | 10 ++++++++--
 arch/loongarch/boot/dts/Makefile |  3 +--
 arch/loongarch/kernel/setup.c    |  9 +++++++--
 4 files changed, 34 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index ee123820a476..267de6191dfc 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -331,6 +331,24 @@  config 64KB_3LEVEL
 
 endchoice
 
+config BUILTIN_DTB
+	bool "Enable builtin dtb in kernel"
+	depends on OF
+	help
+	  Some existing systems do not provide a canonical device tree to the
+	  kernel at boot time. Let's provide a device tree table in the kernel,
+	  keyed by the dts filename, containing the relevant DTBs.
+
+	  Built-in DTBs are generic enough and can be used as references.
+
+config BUILTIN_DTB_NAME
+	string "Source file for LoongArch builtin dtb"
+	depends on BUILTIN_DTB
+	help
+	  Base name (without suffix, relative to arch/loongarch/boot/dts/)
+	  for the DTS file that will be used to produce the DTB linked into the
+	  kernel.
+
 config CMDLINE
 	string "Built-in kernel command line"
 	help
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index 4ba8d67ddb09..5b84f43adb98 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile
@@ -5,7 +5,8 @@ 
 
 boot	:= arch/loongarch/boot
 
-KBUILD_DEFCONFIG := loongson3_defconfig
+KBUILD_DEFCONFIG		:= loongson3_defconfig
+KBUILD_DTBS			:= dtbs
 
 image-name-y			:= vmlinux
 image-name-$(CONFIG_EFI_ZBOOT)	:= vmlinuz
@@ -141,13 +142,16 @@  endif
 
 vdso-install-y += arch/loongarch/vdso/vdso.so.dbg
 
-all:	$(notdir $(KBUILD_IMAGE))
+all:	$(notdir $(KBUILD_IMAGE)) $(KBUILD_DTBS)
 
 vmlinuz.efi: vmlinux.efi
 
 vmlinux.elf vmlinux.efi vmlinuz.efi: vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $(bootvars-y) $(boot)/$@
 
+# device-trees
+core-y += arch/loongarch/boot/dts/
+
 install:
 	$(Q)install -D -m 755 $(KBUILD_IMAGE) $(INSTALL_PATH)/$(image-name-y)-$(KERNELRELEASE)
 	$(Q)install -D -m 644 .config $(INSTALL_PATH)/config-$(KERNELRELEASE)
@@ -155,5 +159,7 @@  install:
 
 define archhelp
 	echo '  install              - install kernel into $(INSTALL_PATH)'
+	echo '  dtbs                 - Device-tree blobs for enabled boards'
+	echo '  dtbs_install         - Install dtbs to $(INSTALL_DTBS_PATH)'
 	echo
 endef
diff --git a/arch/loongarch/boot/dts/Makefile b/arch/loongarch/boot/dts/Makefile
index 5f1f55e911ad..1e24cdb5180a 100644
--- a/arch/loongarch/boot/dts/Makefile
+++ b/arch/loongarch/boot/dts/Makefile
@@ -1,4 +1,3 @@ 
 # SPDX-License-Identifier: GPL-2.0-only
-dtstree	:= $(srctree)/$(src)
 
-dtb-y := $(patsubst $(dtstree)/%.dts,%.dtb, $(wildcard $(dtstree)/*.dts))
+obj-$(CONFIG_BUILTIN_DTB)	+= $(addsuffix .dtb.o, $(CONFIG_BUILTIN_DTB_NAME))
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index d183a745fb85..6cf3b1e045f6 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -295,8 +295,13 @@  static void __init fdt_setup(void)
 	if (acpi_os_get_root_pointer())
 		return;
 
-	/* Look for a device tree configuration table entry */
-	fdt_pointer = efi_fdt_pointer();
+	/* We prefer to try to use built-in dtb, checking its legality first. */
+	if (!fdt_check_header(__dtb_start))
+		fdt_pointer = __dtb_start;
+	else
+		/* Fallback to efi dtb, when built-in dtb is not available. */
+		fdt_pointer = efi_fdt_pointer();
+
 	if (!fdt_pointer || fdt_check_header(fdt_pointer))
 		return;