[PATCH v2 2/2] ARM: move device tree mapping out of linear region

[Joel Stanley]

On Wed, 28 Oct 2020 at 12:53, Ard Biesheuvel <ardb at kernel.org> wrote:
>
> On Wed, 28 Oct 2020 at 13:05, Joel Stanley <joel at jms.id.au> wrote:
> >
> > On Wed, 28 Oct 2020 at 09:19, Marek Szyprowski <m.szyprowski at samsung.com> wrote:
> > > This patch landed in linux-next 20201028 as commit 7a1be318f579 ("ARM:
> > > 9012/1: move device tree mapping out of linear region"). Sadly it broke
> > > booting  almost all Samsung Exynos-based boards. The only one which
> > > booted, used an appended device tree. I can provide more information if
> > > needed, just let me know what to check. "Starting kernel ..." is the
> > > last message I see here. No output from earlycon.
> >
> > A bisection lead me to this patch after the next-20201028 failed to
> > boot on the aspeed systems in testing (aspeed_g5_defconfig).
> >
> > You can reproduce this with today's next and qemu 5.1:
> >
> > qemu-system-arm -M romulus-bmc -nographic \
> >  -kernel arch/arm/boot/zImage \
> >  -dtb arch/arm/boot/dts/aspeed-bmc-opp-romulus.dtb \
> >  -initrd any-old-file
> >
> > It requires the initrd option to reproduce, but the initrd doesn't
> > need to be valid as we don't make it that far.
> >
> > There is no output but attaching gdb shows the kernel is stuck in
> > setup_machine_tags. (If we enable CONFIG_ATAGS it is instead stuck in
> > calibrate_delay).
> >
> > (gdb) bt
> > #0  setup_machine_tags (machine_nr=<optimized out>,
> > __atags_vaddr=<optimized out>) at ../arch/arm/kernel/atags.h:12
> > #1  setup_arch (cmdline_p=0x80c01fc4) at ../arch/arm/kernel/setup.c:1100
> > #2  0x80b00d2c in start_kernel () at ../init/main.c:862
> > #3  0x00000000 in ?? ()
> >
> > Reverting 7a1be318f579 on top of next allowed the system to boot again.
> >
>
> Does this help?

Yes, that boots to userspace.

>
> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
> index bb79e52aeb90..4f355bda872a 100644
> --- a/arch/arm/include/asm/memory.h
> +++ b/arch/arm/include/asm/memory.h
> @@ -68,8 +68,8 @@
>  #define XIP_VIRT_ADDR(physaddr)  (MODULES_VADDR + ((physaddr) & 0x000fffff))
>
>  #define FDT_FIXED_BASE         UL(0xff800000)
> -#define FDT_FIXED_SIZE         (2 * PMD_SIZE)
> -#define FDT_VIRT_ADDR(physaddr)        ((void *)(FDT_FIXED_BASE |
> (physaddr) % PMD_SIZE))
> +#define FDT_FIXED_SIZE         (2 * SECTION_SIZE)
> +#define FDT_VIRT_ADDR(physaddr)        ((void *)(FDT_FIXED_BASE |
> (physaddr) % SECTION_SIZE))
>
>  #if !defined(CONFIG_SMP) && !defined(CONFIG_ARM_LPAE)
>  /*