linux-kernel - Re: 5.15 regression: CONFIG_SYSFB_SIMPLEFB breaks console scrolling

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Date:   Fri, 3 Dec 2021 12:20:25 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Thorsten Leemhuis <regressions@...mhuis.info>,
        Harald Dunkel <harri@...ics.de>
Cc:     Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>
Subject: Re: 5.15 regression: CONFIG_SYSFB_SIMPLEFB breaks console scrolling

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.

Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat