Thinkpad X1 Carbon 3rd - Reducing the compressed framebuffer size

[Pali Rohár]

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:

$ 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