Thinkpad X1 Carbon 3rd - Reducing the compressed framebuffer size

[Pali Rohár]

On Tuesday 13 February 2018 15:27:26 Ville Syrjälä wrote:
> On Tue, Feb 13, 2018 at 09:50:30AM +0100, Pali Rohár wrote:
> > On Tuesday 06 February 2018 16:21:43 Pali Rohár wrote:
> > > Hi! I'm periodically getting following message in dmesg on Lenovo
> > > Thinkpad X1 Carbon 3rd generation:
> > > 
> > > [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.
> > > 
> > > In BIOS I already set GPU size to 512M, but this did not help. Also
> > > update to last BIOS version did not help.
> > > 
> > > So why this message is periodically print in dmesg? And what can I do
> > > with this problem?
> > > 
> > > And why cannot Linux kernel allocate itself more memory for GPU (if BIOS
> > > can/could do that)? Is not 512MB for GPU enough?
> > 
> > And here is output from lspci, which clearly says that 512MB is already
> > set for GPU:
> 
> The PCI BAR size has nothing to do with the size of the stolen memory.
> The BAR just provides a window into the global GTT address space of the
> GPU. Stolen memory is a contiguous chunk of physical memory carved out
> by the BIOS.

Ok, how could I detect how much memory was stolen?

In dmesg I see following lines:

[    0.000000] e820: BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x0000000000057fff] usable
[    0.000000] BIOS-e820: [mem 0x0000000000058000-0x0000000000058fff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000059000-0x000000000008bfff] usable
[    0.000000] BIOS-e820: [mem 0x000000000008c000-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000ab908fff] usable
[    0.000000] BIOS-e820: [mem 0x00000000ab909000-0x00000000abb08fff] type 20
[    0.000000] BIOS-e820: [mem 0x00000000abb09000-0x00000000acbfefff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000acbff000-0x00000000acd7efff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x00000000acd7f000-0x00000000acdfefff] ACPI data
[    0.000000] BIOS-e820: [mem 0x00000000acdff000-0x00000000acdfffff] usable
[    0.000000] BIOS-e820: [mem 0x00000000f80f8000-0x00000000f80f8fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000024dffffff] usable

[    0.000000] Reserving Intel graphics memory at 0x00000000ae000000-0x00000000afffffff

[    0.000000] Memory: 7972840K/8282704K available (6196K kernel code, 1159K rwdata, 2848K rodata, 1408K init, 688K bss, 309864K reserved, 0K cma-reserved)

> The BIOS may or may not provide a knob to change the size
> of the stolen memory.

In BIOS Setup screen I have option to choose GPU memory and I set it to
max 512MB. So this is not the right option...

And why cannot kernel use some continuous check of RAM itself?

> > 
> > $ lspci -v -s 00:02.0
> > 00:02.0 VGA compatible controller: Intel Corporation HD Graphics 5500 (rev 09) (prog-if 00 [VGA controller])
> >         Subsystem: Lenovo HD Graphics 5500
> >         Flags: bus master, fast devsel, latency 0, IRQ 46
> >         Memory at e0000000 (64-bit, non-prefetchable) [size=16M]
> >         Memory at c0000000 (64-bit, prefetchable) [size=512M]
> >         I/O ports at 3000 [size=64]
> >         [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
> >         Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
> >         Capabilities: [d0] Power Management version 2
> >         Capabilities: [a4] PCI Advanced Features
> >         Kernel driver in use: i915
> >         Kernel modules: i915
> > 
> > -- 
> > Pali Rohár
> > pali.rohar at gmail.com
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

-- 
Pali Rohár
pali.rohar at gmail.com