Re: x86: Boot failure on select chromebooks with v6.15-rc5

[Vignesh Raman <vignesh.raman@collabora.com>]

Hi Ingo,

On 09/05/25 11:36, Ingo Molnar wrote:
> 
> * Vignesh Raman <vignesh.raman@collabora.com> wrote:
> 
>> Hi,
>>
>> With v6.15-rc5, the below chromebooks were not booting with the following
>> message. These tests were run in drm-ci.
>>
>> Starting kernel ...
>> [    1.843801]  ? __pfx_kernel_init+0x10/0x10
>> [    1.909838]  ? __pfx_kernel_init+0x10/0x10
>>
>> https://gitlab.freedesktop.org/vigneshraman/linux/-/pipelines/1420485
>>
>> Failing jobs:
>> amdgpu:stoney (AMD Stoney Ridge chipset):
>> https://gitlab.freedesktop.org/vigneshraman/linux/-/jobs/76000926
>>
>> i915:amly (64 bit Intel Whiskey Lake):
>> https://gitlab.freedesktop.org/vigneshraman/linux/-/jobs/76000929
>>
>> i915:whl (64 bit Intel Amber Lake):
>> https://gitlab.freedesktop.org/vigneshraman/linux/-/jobs/76000931
>>
>> These tests were passing till v6.14-rc7, and the issue was seen starting in
>> v6.15-rc1. This issue is seen only with these 3 boards and does not affect
>> other chromebooks (the pipeline log shows the other i915 driver tests).
>>
>> On bisecting the commits, the commit which introduced this issue is,
>> 3181424aeac2f6596534bf43021a10eae294a9b0 x86/early_printk: Add support for
>> MMIO-based UARTs
>>
>> After reverting the below commits in v6.15-rc5, the board boots and tests
>> are executed:
>> 3181424aeac2 x86/early_printk: Add support for MMIO-based UARTs
>> 996457176bb7 x86/early_printk: Use 'mmio32' for consistency, fix comments
>> (this fixes 3181424aeac2)
> 
> What boot cmdline does your kernel have? The MMIO-UART patches should
> only have an effect if the feature is specifically enabled via a boot
> option:
> 
> +               if (!strncmp(buf, "mmio32", 6)) {
> +			buf += 6;
> +                       early_mmio_serial_init(buf);
> +                       early_console_register(&early_serial_console, keep);
> +                       buf += 4;
> +               }
> 

amdgpu:stoney:
earlyprintk=uart8250,mmio32,0xfedc6000,115200n8  console=ttyS0,115200n8 
root=/dev/nfs rw 
nfsroot=192.168.201.1:/var/lib/lava/dispatcher/tmp/18598802/extract-nfsrootfs-wgn1xjer,tcp,hard,v3 
init=/init rootwait usbcore.quirks=0bda:8153:k ip=dhcp 
tftpserverip=192.168.201.1

i915:amly:
earlyprintk=uart8250,mmio32,0xde000000,115200n8  console=ttyS0,115200n8 
root=/dev/nfs rw 
nfsroot=192.168.201.1:/var/lib/lava/dispatcher/tmp/18598804/extract-nfsrootfs-5rlm_b6z,tcp,hard,v3 
init=/init rootwait usbcore.quirks=0bda:8153:k ip=dhcp 
tftpserverip=192.168.201.1

i915:whl:
earlyprintk=uart8250,mmio32,0xde000000,115200n8  console=ttyS0,115200n8 
root=/dev/nfs rw 
nfsroot=192.168.201.1:/var/lib/lava/dispatcher/tmp/18598833/extract-nfsrootfs-3w0w5_mi,tcp,hard,v3 
init=/init rootwait usbcore.quirks=0bda:8153:k ip=dhcp 
tftpserverip=192.168.201.1

Regards,
Vignesh

> The only other change I can see is the moving of an #if line.
> 
> Thanks,
> 
> 	Ingo