Re: [PATCH tty v11 1/2] serial: 8250: Switch to nbcon console, take 2

[Jon Hunter <jonathanh@nvidia.com>]

Hi Petr,

On 18/08/2026 08:51, Petr Mladek wrote:

...

>> This change is causing a boot regression for our Tegra20 and Tegra30
>> platforms. Reverting this on top of -next fixes the issue. Previously with
>> V5 I did not see a boot issue only an issue in suspend. So far I have not
>> had chance to dig any further.
> 
> Interesting.
> 
> Another clue, mentioned in the v9 thread [1], is that the boot
> regression does not happen with v11 when "keep_bootcon" option
> is used.
> 
> The "keep_bootcon" option causes that the boot console driver stays
> registered even when the full featured driver gets registered
> later.
> 
> The most important effect is that the printk kthreads can't
> be used as long as any boot console driver is registered.
> All drivers need to be called in the legacy loop in this case.
> There are two reasons for this:
> 
>    1. Boot console drivers are synchronized only by
>       the legacy console_lock (console_sem). port->lock
>       is available only for the full featured driver.
> 
>    2. There is no easy way to match boot console and
>       full featured console drivers working on the same
>       HW.
> 
> So, the regression seems to happen when the printk kthreads
> start being used.
> 
> Jon, could you please share the full log when "keep_bootcon"
> is used?


Yes absolutely. You can find the boot log here [0]. So far nothing 
really stands out to me but let me know if you see anything.

Jon

[0] https://pastebin.com/FhQVSqfy

-- 
nvpublic