5.15 regression: CONFIG_SYSFB_SIMPLEFB breaks console scrolling

[Thorsten Leemhuis]

Hi, this is your Linux kernel regression tracker speaking.

On 03.12.21 12:20, Javier Martinez Canillas wrote:
> Sorry for the late reply.
> 
> On 11/21/21 12:47, Thorsten Leemhuis wrote:
>> Hi, this is your Linux kernel regression tracker speaking.
>>
>> On 16.11.21 05:52, Harald Dunkel wrote:
>>>
>>> if I enable CONFIG_SYSFB_SIMPLEFB in 5.15.2 and use grub's default
>>> configuration
>>> (Debian sid amd64), then a few lines at the bottom of /dev/tty1 including
>>> login prompt are off-screen. Scrolling is broken. I can login, though.
>>>
>>> Enabling GRUB_TERMINAL=console in grub doesn't make a difference. Using
>>> the same kernel except for CONFIG_SYSFB_SIMPLEFB the problem is gone.
>>>
>>> Graphics card is a GeForce GTX 1650. I tried with both CONFIG_DRM_NOUVEAU
>>> and proprietary graphics drivers disabled.
>>>
>>> Attached you can find the config file. Please mail if I can help to track
>>> this problem down.
>>
>> Thx for the report. I'm not totally sure if this is a regression, as
>> that's a new config option. But it might be one considered a successor
>> to an older one, hence it might count as regression. Adding two
>> developers and a mailing list to the CC, hopefully someone can clarify.
> 
> I don't think this is a regression since enabling CONFIG_SYSFB_SIMPLEFB will
> make the simpledrm driver to be bound while disabling the option makes the
> efifb driver to be bound instead.
>  Yes, it seems to be a bug in the simpledrm driver but the solution if you
> have issues with the simpledrm is to not enable CONFIG_SYSFB_SIMPLEFB and
> keep using the old fbdev driver.

Mandy thx for the answer, Javier. Harald is quiet for some time already
and didn't object so far, hence I'll remove this from regzbot:

#regzbot invalid: problem caused by a new CONFIG option

Ciao, Thorsten

P.S.: As a Linux kernel regression tracker I'm getting a lot of reports
on my table. I can only look briefly into most of them. Unfortunately
therefore I sometimes will get things wrong or miss something important.
I hope that's not the case here; if you think it is, don't hesitate to
tell me about it in a public reply. That's in everyone's interest, as
what I wrote above might be misleading to everyone reading this; any
suggestion I gave they thus might sent someone reading this down the
wrong rabbit hole, which none of us wants.

BTW, I have no personal interest in this issue, which is tracked using
regzbot, my Linux kernel regression tracking bot
(https://linux-regtracking.leemhuis.info/regzbot/). I'm only posting
this mail to get things rolling again and hence don't need to be CC on
all further activities wrt to this regression.