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

[Ingo Molnar <mingo@kernel.org>]

* 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;
+               }

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

Thanks,

	Ingo