On Tue, 10 Oct 2023 at 10:40, Stephan Gerhold <stephan@xxxxxxxxxxx> wrote: > > On Mon, Oct 09, 2023 at 08:27:17PM +0300, Dmitry Baryshkov wrote: > > On Qualcomm platforms the bootloader populates device tree with some > > extra nodes / properties (like memory size, boot time, etc). Usually > > default padding is enough for the bootloader. But in some cases the > > board will fail to boot if there is not enough padding space. > > > > Add `--pad 4096' to DTC_FLAGS so that all Qualcomm DTB files get this > > extra padding space. > > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > > --- > > > > This is primarily necessary for SA8155P, but I have the feeling that it > > might be better to be enabled on the global scale. > > By default there should not be any padding at all. This is because the > bootloader is responsible to make room for new nodes by calling > fdt_open_into() with an adjusted size. This will result in a simple > memmove() that shifts the end of the DTB in memory so that the padding > can be used for new nodes and properties. > > If the bootloader doesn't add enough padding then it is broken and > should be fixed. Several other platforms use --pad, see microblaze, openrisc and powerpc. In some cases we just can not update the bootloader. > > Both LK [1] and ABL [2] do or have done this correctly at some point. > If more space is needed for some weird new modifications the padding > size there should be adjusted. > > [1]: https://git.codelinaro.org/clo/la/kernel/lk/-/blob/lk.lnx.1.0.r54-rel/platform/msm_shared/dev_tree.c#L2051-2057 > [2]: https://git.codelinaro.org/clo/la/abl/tianocore/edk2/-/blob/uefi.lnx.4.0.r40-rel/QcomModulePkg/Library/BootLib/UpdateDeviceTree.c#L1402-1414 In this case ABL fails to handle the situation: Cmdline: ignore_loglevel console=tty0 console=ttyMSM0,115200n8 earlycon root=PARTLABEL=rootfs rootwait adbd -- androidboot.verifiedbootstate Error adding node Error carving out UEFI memory: FFFFFFFF Adding --pad 1024 is enough for this board to boot. > > By adding --pad 4096 globally we would waste pointless empty space for > every single DTB, which ends up on all systems that use generic kernels > with Qualcomm support included. With the ~230 DTBs we have at the moment > this would already waste ~1 MiB (~16 MiB -> ~17 MiB total). > > So please: > > - If you can, update the bootloader and fix the padding size there. > > - If this is not possible: Add the padding only for the boards with > broken bootloaders with a clear comment that this should be the last > resort for devices that are locked down. Yep, this sounds like the correct approach in this case. Thank you. > > - Or maybe boot a less broken bootloader inbetween (like U-Boot). :) > > Thanks, > Stephan > > > > > --- > > arch/arm64/boot/dts/qcom/Makefile | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/arch/arm64/boot/dts/qcom/Makefile b/arch/arm64/boot/dts/qcom/Makefile > > index d6cb840b7050..8e9fa2539265 100644 > > --- a/arch/arm64/boot/dts/qcom/Makefile > > +++ b/arch/arm64/boot/dts/qcom/Makefile > > @@ -1,4 +1,8 @@ > > # SPDX-License-Identifier: GPL-2.0 > > + > > +# pad DT allowing bootloader to populate several extra nodes > > +DTC_FLAGS += --pad 4096 > > + > > dtb-$(CONFIG_ARCH_QCOM) += apq8016-sbc.dtb > > > > apq8016-sbc-usb-host-dtbs := apq8016-sbc.dtb apq8016-sbc-usb-host.dtbo > > -- > > 2.39.2 > > -- With best wishes Dmitry
