On Mon, Sep 28, 2026 at 7:53 PM Quentin Schulz <[email protected]> wrote: > > > > On 9/28/26 4:03 PM, Alexey Charkov wrote: > > Hi Quentin, > > > > On Mon, Sep 28, 2026 at 5:26 PM Quentin Schulz <[email protected]> > > wrote: > >> > >> Hi Alexey, > >> > >> On 7/31/26 7:10 PM, Alexey Charkov wrote: > >>> When a generated FIT is used to boot Linux directly, bypassing U-Boot > >>> proper (Falcon mode), there is no runtime code to discover the kernel > >>> command line and (optional) initrd location and include them in a FDT. > >>> > >>> To facilitate easier preparation of a ready-to-boot FIT, add support for > >>> pre-patching the FDTs in a FIT with a preconfigured /chosen node including > >>> the bootargs and initrd location. > >>> > >> > >> This sounds wrong to me. Why should we hardcode those at build time? We > >> already do DT fixups in U-Boot proper *at runtime*, so we should > >> probably do the same in xPL when booting in Falcon mode instead of > >> hardcoding stuff. Since you're aware of this, I'm guessing you decided > >> against, but you don't tell us why. I'm a bit worried going with the > >> suggested implementation means we'll eventually have a binman node > >> property for each DT node/property we want to write/override. > > > > The "regular" Falcon way of doing things (i.e. the one not involving > > TF-A) has so far been: "capture what U-Boot patches into the args to > > be passed to the kernel, package it into a fixed binary, and boot only > > that". No runtime fixups. So I more or less followed that pattern, but > > tried to make it a bit more accessible by eliminating the "capture > > something at runtime and save it somehow somewhere" step, which I find > > unnecessarily painful. > > > > Maybe runtime fixups could be brought into xPL, but they are > > excruciatingly slow, whereas speed is the main reason for wanting > > Falcon mode boot in the first place. Right now with Falcon mode on > > RK3576 I'm getting 2.5 seconds from applying power to _userspace_ > > (i.e. full graphical UI drawn on the screen), whereas the best I could > > get with U-Boot is just over 3s to its boot menu, much of that time > > spent going over the flat devicetree before relocation in O(n^2) > > passes. And those 3s are after stripping the massive pinctrl node with > > hundreds of its always-present children from the pre-relocation DT, > > which alone saves ~0.4s. > > > > Are they always present, even with /omit-if-no-ref/ instruction? Or > maybe you're building the device trees with -@? Trying to figure out if > somehow we have a bug in dtc (or in our scripts making use of it).
The problem is that there are a lot of `status = "disabled";` device nodes referencing pinctrl nodes, which keep dtc from dropping them altogether, so a lot of unused pin configs end up in the binary - enough to be noticeable in boot time. > Don't we have FDT and DM in SPL anyway as that's how we probe drivers in > that stage (not counting the few SPL-only boards we have)? SPL's DTB is tiny due to bootph-* markup (it was just 27 nodes last time I counted for my RK3576 use case). Making SPL parse the whole OS-oriented device tree, along with all the relocations required to insert stuff at runtime, will hurt. > I don't have anything better to suggest, I'm just really worried about > the potential ballooning of properties we need to mirror in binman. > > >>> Signed-off-by: Alexey Charkov <[email protected]> > >>> --- > >>> tools/binman/entry.py | 8 ++++ > >>> tools/binman/etype/fit.py | 103 > >>> ++++++++++++++++++++++++++++++++++++++++++++++ > >>> 2 files changed, 111 insertions(+) > >>> > >>> diff --git a/tools/binman/entry.py b/tools/binman/entry.py > >>> index ce7ef28e94b1..e0dea8bf3a49 100644 > >>> --- a/tools/binman/entry.py > >>> +++ b/tools/binman/entry.py > >>> @@ -636,6 +636,14 @@ class Entry(object): > >>> self.Detail('GetData: size %s' % to_hex_size(self.data)) > >>> return self.data > >>> > >>> + def GetNode(self): > >>> + """Get the devicetree node which describes this entry > >>> + > >>> + Returns: > >>> + Node: Node for this entry > >>> + """ > >>> + return self._node > >>> + > >>> def GetPaddedData(self, data=None): > >>> """Get the data for an entry including any padding > >>> > >>> diff --git a/tools/binman/etype/fit.py b/tools/binman/etype/fit.py > >>> index 32caa03a7e16..750ff5b47ed5 100644 > >>> --- a/tools/binman/etype/fit.py > >>> +++ b/tools/binman/etype/fit.py > >>> @@ -304,6 +304,40 @@ class Entry_fit(Entry_section): > >>> > >>> See :ref:`fdtgrep_filter` for more information. > >>> > >>> + Patching /chosen into the generated device trees > >>> + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > >>> + > >>> + When the OS is booted directly from this FIT (e.g. Falcon mode) > >>> U-Boot > >>> + proper never runs, so its usual runtime /chosen fixups do not > >>> happen. Two > >>> + optional properties on the `@fdt-SEQ` node make binman patch each > >>> generated > >>> + device tree at build time: > >>> + > >>> + fit,bootargs > >>> + A string written to /chosen/bootargs of every generated device > >>> tree > >>> + (any existing value is overwritten). Typically set to > >>> `CONFIG_BOOTARGS` > >>> + via the preprocessed devicetree source. > >>> + > >>> + fit,initrd > >>> + The image name of a loadable (e.g. "ramdisk") to use as the > >>> initramfs. > >>> + Its `load` address and packed size are written to > >>> + /chosen/linux,initrd-start and /chosen/linux,initrd-end (at the > >>> width of > >>> + the device tree's root #address-cells) and reserved in the FDT > >>> + memory-reservation map, mirroring fdt_initrd(). If the > >>> referenced image > >>> + is absent or empty (e.g. an optional initramfs that was not > >>> supplied) > >>> + the initrd properties are omitted. > >>> + > >> > >> This sounds wrong, why would the FDT image node need to know about which > >> ramdisk may be used? Shouldn't we rather have a ramdisk property in a > >> configuration node, and then patch the FDT based on that information? > > > > Falcon mode boot where these are useful is for a fixed-configuration > > boot flow anyway, where one wouldn't have a way to select among > > How do you plan on doing A/B with Falcon boot? How do you know from > which partition the kernel you booted originated so you don't upgrade on > the currently booted partition? There must be some way for U-Boot SPL to > tell the kernel at runtime where it came from? I don't currently do A/B with Falcon; instead, I rely on the fallback to U-Boot, and U-Boot in turn loads from a UFS boot W-LU (which is A/B native). Making A/B work with Falcon would be a nice follow-up, but I believe it will require some external metadata to choose the active boot source anyway - and then the same external metadata can be used for the upgrade. Such as the UFS device attributes, or whatever people use for RAUC and such. > > several ramdisks to go with the kernel image. So putting this > > information directly where the user (i.e. the kernel) will find it > > cuts out intermediate steps, which in turn improves speed and reduces > > complexity. > > You already have: > > fit,firmware = "atf-1", "kernel", "ramdisk"; > fdt = "fdt-SEQ"; > > in the configuration node. So simply have binman derive from > fit,firmware which node is included of type "ramdisk" and fixup the > device trees in fdt-SEQ based on that info? Less user-prone IMO. Ah, I thought you were referring to runtime FDT fixups based on the selected configuration. Patching it in using binman based on the configuration node contents should work, too, but what's the practical benefit? It would still use the same ramdisk node, just written in a different place - or am I missing something? Best regards, Alexey
