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

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

Hi Ingo,

On 09/05/25 12:07, Ingo Molnar wrote:
> 
> * Vignesh Raman <vignesh.raman@collabora.com> wrote:
> 
>>> 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
> 
> Well, if you remove the earlyprintk option then it will boot fine,
> right?

Yes, it works when mmio32 option is removed.

https://gitlab.freedesktop.org/vigneshraman/linux/-/jobs/76005338

earlyprintk=uart8250,0xde000000,115200n8  console=ttyS0,115200n8 
root=/dev/nfs rw 
nfsroot=192.168.201.1:/var/lib/lava/dispatcher/tmp/18599938/extract-nfsrootfs-neuejjq0,tcp,hard,v3 
init=/init rootwait usbcore.quirks=0bda:8153:k ip=dhcp 
tftpserverip=192.168.201.1

> 
> The earlyprintk=mmio32 in v6.15 is a new debugging feature that was
> tested on a single board by Denis Mukhin AFAIK, and it may or may not
> work on your particular UART - even assuming that all the parameters
> are correct.

So the earlyprintk=mmio32 debugging feature is needed only for v6.15 and 
is not necessary in previous kernels (e.g., v6.14 and earlier). Is my 
understanding correct?

Regards,
Vignesh

> 
> Thanks,
> 
> 	Ingo