On Thu, Sep 05, 2024 at 08:47:39AM +0900, Masahiro Yamada wrote: > Some architectures support embedding boot DTB(s) in vmlinux. These > architectures, except MIPS and MicroBlaze, expect a single DTB in > the .dtb.init.rodata section. MIPS embeds multiple DTBs in vmlinux. > MicroBlaze embeds a DTB in its own __fdt_blob section instead of the > .dtb.init.rodata section. > > For example, RISC-V previously allowed embedding multiple DTBs, but > only the first DTB in the .dtb.init.rodata section was used. Commit > 2672031b20f6 ("riscv: dts: Move BUILTIN_DTB_SOURCE to common Kconfig") > ensured only one boot DTB is embedded. > > Meanwhile, commit 7b937cc243e5 ("of: Create of_root if no dtb provided > by firmware") introduced another DTB into the .dtb.init.rodata section. > > The symbol dump (sorted by address) for ARCH=riscv nommu_k210_defconfig > is now as follows: > > 00000000801290e0 D __dtb_start > 00000000801290e0 D __dtb_k210_generic_begin > 000000008012b571 D __dtb_k210_generic_end > 000000008012b580 D __dtb_empty_root_begin > 000000008012b5c8 D __dtb_empty_root_end > 000000008012b5e0 D __dtb_end > > The .dtb.init.rodata section contains the following two DTB files: > > arch/riscv/boot/dts/canaan/k210_generic.dtb > drivers/of/empty_root.dtb > > This is not an immediate problem because the boot code chooses the > first DTB, k210_generic.dtb. The second one, empty_root.dtb is ignored. > However, relying on the link order (i.e., the order in Makefiles) is > fragile. > > Only the boot DTB should be placed in the .dtb.init.rodata because the > arch boot code generally does not know the DT name, thus it uses the > __dtb_start symbol to find it. > > empty_root.dtb is looked up by name, so it can be moved to the generic > .init.rodata section. > > When CONFIG_OF_UNITTEST is enabled, more unittest DTBOs are embedded in > the .dtb.init.rodata section. These are also looked up by name, so can > be moved to the .init.rodata section. > > I added the __initdata annotation to the overlay_info data array because > modpost knows the .init.rodata section is discarded, and would otherwise > warn about it. > > The implementation is kind of cheesy; the section is .dtb.init.rodata > under the arch/ directory, and .init.rodata section otherwise. This will > be refactored later. > > Signed-off-by: Masahiro Yamada <masahi...@kernel.org> > --- > > drivers/of/unittest.c | 2 +- > scripts/Makefile.dtbs | 4 +++- > 2 files changed, 4 insertions(+), 2 deletions(-)
Reviewed-by: Rob Herring (Arm) <r...@kernel.org> _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc