Re: Fail to bring hart online on HiFive Unleashed

[Aurelien Jarno <aurelien@aurel32.net>]

Le 8 octobre 2019 08:14:58 GMT+02:00, David Abdurachmanov <david.abdurachmanov@sifive.com> a écrit :
>On Tue, Oct 8, 2019 at 7:30 AM Aurelien Jarno <aurelien@aurel32.net>
>wrote:
>>
>> On 2019-10-07 22:19, Atish Patra wrote:
>> > Thanks for the detailed analysis. Can you please keep me and david
>in
>> > cc when you report the issue to U-boot ?
>>
>> Yep. I have progressed a bit on that, and now I am not convinced it's
>an
>> U-boot issue, it can be a GCC issue.
>>
>> Here are the conditions to reproduce the bug:
>> - U-boot runs on hart 1, 2 or 3
>> - the autoboot process is not interrupted
>> - extlinux is used to boot the kernel
>> - arch/riscv/lib/bootm.c is compiled with GCC 9 (works fine with GCC
>8)
>>
>> When the problem happens, the missing hart actually ends its
>execution
>> in an illegal instruction trap trying to execute the FDT (I only
>noticed
>> that recently as the message was hidden by the use of earlycon=sbi):
>>
>> | SiFive FSBL:       2018-03-20
>> | HiFive-U serial #: 00000246
>> |
>> | OpenSBI v0.4-50-g30f09fb (Oct  6 2019 21:58:05)
>> |    ____                    _____ ____ _____
>> |   / __ \                  / ____|  _ \_   _|
>> |  | |  | |_ __   ___ _ __ | (___ | |_) || |
>> |  | |  | | '_ \ / _ \ '_ \ \___ \|  _ < | |
>> |  | |__| | |_) |  __/ | | |____) | |_) || |_
>> |   \____/| .__/ \___|_| |_|_____/|____/_____|
>> |         | |
>> |         |_|
>> |
>> | Platform Name          : SiFive Freedom U540
>> | Platform HART Features : RV64ACDFIMSU
>> | Platform Max HARTs     : 5
>> | Current Hart           : 2
>> | Firmware Base          : 0x80000000
>> | Firmware Size          : 104 KB
>> | Runtime SBI Version    : 0.2
>> |
>> | PMP0: 0x0000000080000000-0x000000008001ffff (A)
>> | PMP1: 0x0000000000000000-0x0000007fffffffff (A,R,W,X)
>> |
>> |
>> | U-Boot 2019.10-rc4-00037-gdac51e9aaf-dirty (Oct 06 2019 - 21:56:51
>+0000)
>> |
>> | CPU:   rv64imafdc
>> | Model: SiFive HiFive Unleashed A00
>> | DRAM:  8 GiB
>> |
>> | MMC:   spi@10050000:mmc@0: 0
>> | In:    serial@10010000
>> | Out:   serial@10010000
>> | Err:   serial@10010000
>> | Net:   eth0: ethernet@10090000
>> | Hit any key to stop autoboot:  0
>> | switch to partitions #0, OK
>> | mmc0 is current device
>> | Scanning mmc 0:2...
>> | Found /boot/extlinux/extlinux.conf
>> | Retrieving file: /boot/extlinux/extlinux.conf
>> | 510 bytes read in 5 ms (99.6 KiB/s)
>> | U-Boot menu
>> | 1:      kernel 5.3.4
>> | 2:      Debian GNU/Linux kernel 5.3.0-trunk-riscv64
>> | Enter choice: 1
>> | 1:      kernel 5.3.4
>> | Retrieving file: /boot/vmlinux-5.3.4
>> | 9486076 bytes read in 4813 ms (1.9 MiB/s)
>> | append: root=/dev/mmcblk0p2 rw console=ttySIF0 rootwait
>> | Retrieving file: /boot/hifive-unleashed-a00.dtb
>> | 6088 bytes read in 7 ms (848.6 KiB/s)
>> | ## Flattened Device Tree blob at 88000000
>> |    Booting using the fdt blob at 0x88000000
>> |    Using Device Tree in place at 0000000088000000, end
>00000000880047c7
>> |
>> | Starting kernel ...
>> |
>> | exception code: 2 , Illegal instruction , epc  , ra 88000004
>88000000
>> | ### ERROR ### Please RESET the board ###
>
>I think, that's the same issue I had (or still have) a week ago.
>Just reminder that kernel 5.3 introduced a 64-byte header (thus no
>need to wrap kernel) at least for Image target. Thus it's booti that
>boots the kernel on U-Boot side.
>Thus the 1st instruction of that header is "j 0x40" (to the beginning
>of the actual kernel).  And 88000004 would definitely hold an illegal
>instruction.
>
>0000000000000000 <.data>:
>0:       81a0                    j       0x40
>2:       0000                    unimp
>4:       0000                    unimp
>6:       0100                    nop
>[..]

Hmm that's the beginning of the kernel code. The address 88000004
actually corresponds to the FDT. So the hart ending up in a trap
actually tries to boot the FDT instead of the kernel.

I haven't spotted any obvious differences between bootm.o compiled with
GCC 8 and GCC 9. I wonder if there is somehow a race condition because
some harts are already executing linux while the last one is still
executing U-boot.

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv