[Regression] No framebuffer console on Rpi since 5.14-rc1

[Maxime Ripard]

Hi Stefan,

On Wed, Jul 28, 2021 at 05:14:38PM +0200, Stefan Wahren wrote:
> Hi,
> 
> Am 15.07.21 um 18:35 schrieb Stefan Wahren:
> > Hi guys,
> >
> > starting with Linux 5.14-rc1 the framebuffer console on Raspberry Pi 3/4
> > (no U-Boot, multi_v7_defconfig) isn't available anymore. The display
> > shows the rainbow screen from the bootloader and than the HDMI screen
> > goes black instead of kernel messages.
> >
> > I bisected the issue:
> >
> > 62fb9874f5da54fdb243003b386128037319b219 good
> > e73f0f0ee7541171d89f2e2491130c7771ba58d3 bad
> > e058a84bfddc42ba356a2316f2cf1141974625c9 bad
> > a6eaf3850cb171c328a8b0db6d3c79286a1eba9d good
> > 007b312c6f294770de01fbc0643610145012d244 good
> > 18703923a66aecf6f7ded0e16d22eb412ddae72f good
> > 334200bf52f0637a5ab8331c557dfcecbb9c30fa bad
> > c707b73f0cfb1acc94a20389aecde65e6385349b bad
> > caa18dd6dd9305d52943a6b59f410cbc960ad0a0 good
> > 691cf8cd7a531dbfcc29d09a23c509a86fd9b24f bad
> > 2fdcb55dfc86835e4845e3f422180b5596d23cb4 bad
> > 6c3f953381e526a1623d4575660afae8b19ffa20 bad
> > 5ea4dba68305d9648b9dba30036cc36d4e877bca bad
> > 4a888ba03fd97d1cb0253581973533965bf348c4 good
> > c5ef15ae09637fb51ae43e1d1d98329d67dd4fd6 good
> > f611b1e7624ccdbd495c19e9805629e22265aa16 bad
> > ff323d6d72e1e4971c8ba9e2f3cf8afc48f22383 good
> >
> > f611b1e7624ccdbd495c19e9805629e22265aa16 is the first bad commit
> > commit f611b1e7624ccdbd495c19e9805629e22265aa16
> > Author: Kees Cook <keescook at chromium.org>
> > Date:   Wed Jun 2 14:52:50 2021 -0700
> >
> >     drm: Avoid circular dependencies for CONFIG_FB
> >    
> >     When cleaning up other drm config dependencies, it is too easy to create
> >     larger problems. Instead, mark CONFIG_FB as a "depends":
> >    
> >     drivers/gpu/drm/Kconfig:74:error: recursive dependency detected!
> >
> > I compared the changes to the config (based on multi_v7_defconfig) with
> > and without this patch and it shows a lot of changes. Is this intended?
> 
> just one question: does the VC4 drm driver functionally depend on
> CONFIG_FB / FRAMEBUFFER_CONSOLE ?

No, just the fbdev emulation but it can work perfectly fine without it.

> Or with other words should we re-enable CONFIG_FB like this [1] but for
> Raspberry Pi related configs?
> 
> [1] -
> https://lore.kernel.org/linux-samsung-soc/20210611100204.6240-1-m.szyprowski@samsung.com/

It should work indeed

Maxime
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