[drm] Reducing the compressed framebuffer size

[Ville Syrjälä]

On Tue, May 12, 2020 at 03:36:01PM +0200, Massimo B. wrote:
> Hello everybody,
> 
> since Kernel 5.6.5 I encounter many syslog lines like
> 
> [kernel] [drm] Reducing the compressed framebuffer size. This may lead to less power savings than a non-reduced-size. Try to increase stolen memory size if available in BIOS.
>                 - Last output repeated 4 times -
> 
> I found some explanation at:
> https://wiki.archlinux.org/index.php/intel_graphics#Framebuffer_compression_(enable_fbc)
> But why do I get this with a i7-4790 Haswell, which is not pre-Sandy?

FBC is a thing for all platform generations.

> 
> Anyway I followed the hint and set
> 
> # cat /etc/modprobe.d/i915.conf
> options i915 enable_fbc=0
> 
> After reboot the setting seems active:
> 
> # cat /sys/module/i915/parameters/enable_fbc
> 0
> 
> But I still get the same logs. Which BIOS setting is responsible, how can I fix
> that? Is there a better place to ask?

There is a patch on its way somewhere to linus/stable trees to eliminate
this dmesg spam:
https://cgit.freedesktop.org/drm-intel/commit/?id=6b7fc6a3e6af4ff5773949d0fed70d8e7f68d5ce

But it's a bit strange you still get it with fbc disabled. The logic
for when to allocate the cfb may be a bit busted atm...

> 
> # lspci |grep VGA
> 00:02.0 VGA compatible controller: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor Integrated Graphics Controller (rev 06)
> 
> # grep name /proc/cpuinfo |tail -n1
> model name	: Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz
> 
> Best regards,
> Massimo
> 
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-- 
Ville Syrjälä
Intel