Date: Fri, 11 Aug 2017 11:35:35 +0200 From: Sylvain Garrigues <sylvain@sylvaingarrigues.com> To: Mark Millard <markmi@dsl-only.net> Cc: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: armv6 kernel support for Raspberry Pi 3 in default aarch32 mode Message-ID: <CAKT8nAjguFYBg3VD8%2BQRhK6PntOdP-GJX2WRxqVAGxqmnpzYqA@mail.gmail.com> In-Reply-To: <11C8C2C2-02FA-493A-816E-5ED0653EAF78@dsl-only.net> References: <CAKT8nAiUYBOzvCoHz_rx4npMVvisqQgQLX1jRWhYzq5hk6wcGQ@mail.gmail.com> <AA7A410C-CED5-48C5-B62F-1FCD679DF317@dsl-only.net> <CAKT8nAgciFjG2iBVCFnUEQEMQ94mi80Sk%2BH_qmG_V31V=ks%2BJg@mail.gmail.com> <8910A9FB-E936-4576-97B1-B2EDCB1ED1AE@dsl-only.net> <CAKT8nAiJBv5mRKPfoiENkw%2B_Vur__AcaK-W%2BDtc50Dgk5_D=3w@mail.gmail.com> <11C8C2C2-02FA-493A-816E-5ED0653EAF78@dsl-only.net>
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Actually, with latest u-boot and static RPI2 DTB embedded in kernel, I've managed to make the RPI2 kernel boot on my RPI3 and recognize all cortex-a53 processors. I've got errors then because the DTB mustn't be static, the RPI firmware patches it with required values before giving control to kernel. I still need to figure out why the kernel doesn't like the DTB provided by firmware when it's not static, and panics with "OF_init failed with the found device tree" in initarm, but apart from that I feel like we are close to having a 32-bit OS for RPI3 and new RPI2 v1.2. Copyright (c) 1992-2017 The FreeBSD Project. Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994 The Regents of the University of California. All rights reserved. FreeBSD is a registered trademark of The FreeBSD Foundation. FreeBSD 12.0-CURRENT #45 14d0c5770e7(master)-dirty: Fri Aug 11 17:31:04 CEST 2017 root@box.sylvaingarrigues.com:/usr/obj/arm.armv6/usr/src/sys/GENERIC arm FreeBSD clang version 5.0.0 (branches/release_50 309439) (based on LLVM 5.0.0svn) VT: init without driver. CPU: ARM Cortex-A53 r0p4 (ECO: 0x00000080) CPU Features: Multiprocessing, Thumb2, Security, Virtualization, Generic Timer, VMSAv7, PXN, LPAE, Coherent Walk Optional instructions: SDIV/UDIV, UMULL, SMULL, SIMD(ext) LoUU:2 LoC:3 LoUIS:2 Cache level 1: 32KB/64B 4-way data cache WB Read-Alloc Write-Alloc 32KB/64B 2-way instruction cache Read-Alloc Cache level 2: 512KB/64B 16-way unified cache WB Read-Alloc Write-Alloc ... 2017-08-10 18:04 GMT+02:00 Mark Millard <markmi@dsl-only.net>: > On 2017-Aug-10, at 6:51 AM, Sylvain Garrigues <sylvain at > sylvaingarrigues.com> wrote: > > > 2017-08-10 1:58 GMT+02:00 Mark Millard <markmi@dsl-only.net>: > >> Overall: Supporting aarch32 is not automatic > >> even if one starts from armv7 or specifically > >> a cortex-a53 context unless one was lucky > >> enough to happen to not touch or depend on > >> any of the differences at any stage. > > > > Thanks. I guess though that it's quite easily feasible for someone > familiar with arm lower level initialization. > > > > I can see NetBSD managed to make the armv7 kernel boot on Raspberry Pi 3 > with one commit: > > Get the RPI3 working (in aarch32 mode) by recognising Cortex A53 CPUs. - > https://github.com/IIJ-NetBSD/netbsd-src/commit/ > 00335f7adc380a125d045279c1a0f5525fb557da > > Interesting. > > > Same for OpenBSD folks: > > http://marc.info/?l=openbsd-tech&m=145692659524971&w=2 > > This one (OpenBSD) says (note the "including some other > (still) local diffs"): > > "This way, and including some other (still) local diffs, I have > the brand new raspberry Pi 3 in multiuser: http://ix.io/oJV " > > So the reference only has some of of the code changes shown. > > And the boot log shows: > > cpu0 at mainbus0: ARM Cortex A53 rev 4 (ARMv7 core) > cpu0: DC enabled IC enabled WB disabled EABT branch prediction enabled > cpu0: 32KB(64b/l,2way) I-cache, 32KB(64b/l,4way) wr-back D-cache > > So just one cpu. But for all I know OpenBSD might not have > been SMP capable on a rpi2 at the time either. > > The boot log also shows: > > gpio at bcmgpio0 not configured > broadcom0: device bcmsdhc unit 0 not found > > > So for OpenBSD the code change shown was just the start of the > update as far as I can tell. > > > Plus FreeBSD's RPI2 armv6 kernel does boot and recognize the cortex-a53 > with qemu-aarch64: > > qemu-system-aarch64 -M raspi2 -cpu cortex-a53 -m 1024 -smp 4 -kernel > kernel.bin -serial stdio -dtb rpi2.dtb > > Interesting. How clean is the boot log? > > At least for raspbian there were separate files for rpi3 > when rpi3 was first supported: > > arch/arm/boot/dts/bcm2710-rpi-3-b.dts > arch/arm/boot/dts/bcm2710.dtsi > > Later there was: > > arch/arm/boot/dts/overlays/pi3-disable-bt-overlay.dts > arch/arm/boot/dts/overlays/pi3-miniuart-bt-overlay.dts > arch/arm/boot/dts/overlays/pi3-disable-wifi-overlay.dts > arch/arm/boot/dts/overlays/pi3-act-led-overlay.dts > > as well as some updates to some of those files. (I'm > not sure that I found all such files that are rpi3 > specific [possibly covering rpi2v1.2 as well?].) > > I suspect the qemu-system-aarch64 use is simulating > a rpi2's details as listed in rpi2.dtb instead of the > rpi3's details. (But using a cortex-a53 CPU model.) > There may well be work in supporting the rpi3's > details in the kernel and/or boot loading stages for > all I know. > > What happens if a rpi3 dtb file is used instead of > rpi2.dtb ? > > > > So I guess we too are really not far to boot RPI2 "armv6" kernel on > raspberry pi 2 v1.2 and raspberry pi 3. > > I wish I could help. > > Since I'm finding these things as I go I've no clue > what I've not found. So I can not tell how close to > correct you are. > > > === > Mark Millard > markmi at dsl-only.net > > > >
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