Test T440p with Coreboot NO_GFX_INIT

[rbreslow]

From Coreboot's src/device/Kconfig:

Select this to not perform any graphics initialization in coreboot. This is useful if the payload (e.g. SeaBIOS) can initialize graphics or if pre-boot graphics are not required.

@tlaurion says that the Linux kernel should be able to perform this initialization: #1282 (comment). It's possible that allowing Coreboot to initialize graphics as well is redundant/increases boot times.

The pull request should provide before and after cbmem timings.

Waiting on #1282

[srgrint]

I can confirm I have tried with NO_GFX_INIT set with no adverse effects. For some reason, it still dosen't redraw the screen after the kexec until the deian kernel starts - not quite sure why.

Here it the cbmem log (have built using coreboot 4.19, although 4.17 has the same behaviour)

coreboot_t440p_no_gfx-init.log

[srgrint]

Also as a side issue regarding fine tuning the t440p kernel config, it is possible to safely remove CONFIG_DRM_AST=y

(I think this was a leftover for when the kernel config was cloned from the common librem kernel - in order to make it work with their server boards - clearly not needed on the t440p)

[rbreslow]

I think this was a leftover for when the kernel config was cloned from the common librem kernel [...]

Definitely. I had evaluated all of the Coreboot defaults, but there were too many kernel config options to try and understand each one.

Maybe we open another issue to try and come up with a process for auditing kernel config options?

[tlaurion]

I can confirm I have tried with NO_GFX_INIT set with no adverse effects. For some reason, it still dosen't redraw the screen after the kexec until the deian kernel starts - not quite sure why.

The kexec'ed OS will take over the screen only when and if i915/another fb driver initializes the display. That can be before/after plymouth.

This is where igfx init from coreboot (or no ifgx_init) should create a difference.

[tlaurion]

For example, it is known that installing Archlinux will require end users to add i915 into its initrd.

Never tested archlinux with igfx on on coreboot. That is actually a good test case for this and will try.

[srgrint]

The kexec'ed OS will take over the screen only when and if i915/another fb driver initializes the display. That can be before/after plymouth.

This is where igfx init from coreboot (or no ifgx_init) should create a difference.

Thanks - I wonder whether it is that my version of debian on the HDD is fairly old (version 10 rather than 11). Perhaps older versions didn't add enough to the initramfs. I'll try and upgrade and see what happens.

[srgrint]

Just providing some metrics about adding NO_GFX_INIT to the t440p build. The size of the ramstage is reduced from 120925 to 99316 - so a saving in the CBFS of 21609 bytes.

Clearly as the ramstage is LZMA compressed, the saving when loaded into RAM would be over twice this value. But we care mostly care about CBFS space which is the more precious commodity.

I'll do some timing tests tomorrow with and without NO_GFX_INIT

[srgrint]

So have compared timings.

Without NO_GFX_INIT (so both libgfxinit and linux kernel initialising graphics) - takes 9037ms
With NO_GFX_INIT (so only linux kernel initialising graphics) - takes 8788ms

So by setting NO_GFX_INIT, saves 248ms

I have attached the cbmemc -t logs for both the builds

cbmemc_withoutgraphics.log
cbmemc_withgraphics.log

[srgrint]

The kexec'ed OS will take over the screen only when and if i915/another fb driver initializes the display. That can be before/after plymouth.
This is where igfx init from coreboot (or no ifgx_init) should create a difference.

Thanks - I wonder whether it is that my version of debian on the HDD is fairly old (version 10 rather than 11). Perhaps older versions didn't add enough to the initramfs. I'll try and upgrade and see what happens.

I've upgraded my debian install. All works fine now - presumably my very old debian install didn't have the i915 driver in the initramfs or something.

The behaviour of my T440p is the same as my X230 now from a graphics point of view when NO_GFX_INIT is set

[tlaurion]

@srgrint thanks for #1326

My main question in link to having NO_GFX_INIT set is that OSes known to offer i915+drm drivers into initramfs will boot and have graphics as early as the kexec'ed kernel taking over graphics.

But for OSes not packing i915+drm, does coreboot GFX init (text/framebuffer support) permit to have a terminal on kexec'ed kernel prior of i915+drm and whn none are part of the initrd?

Basically: is coreboot gfx init useful for OSes not supporting specific graphic cards directly in their initramfs?
The question is not targeted specifically for t440p, but related to #1293

[akunterkontrolle]

@srgrint thanks for #1326

My main question in link to having NO_GFX_INIT set is that OSes known to offer i915+drm drivers into initramfs will boot and have graphics as early as the kexec'ed kernel taking over graphics.

But for OSes not packing i915+drm, does coreboot GFX init (text/framebuffer support) permit to have a terminal on kexec'ed kernel prior of i915+drm and whn none are part of the initrd?

Basically: is coreboot gfx init useful for OSes not supporting specific graphic cards directly in their initramfs? The question is not targeted specifically for t440p, but related to #1293

For me, NO_GFX_INIT not set (as it was/is currently) doesn't help at all with kernels that don't have i915-drivers. I have the same problem with Debian showing no graphics at early boot stage. This creates three problems for me:

• The normal Debian installers don't work. Only way to install is via live cd, however the installer than offered lacks severely in features and options.
• No chance of seeing early kernel output to debug problems.
• Memtest doesnt work. That's the most pressing problem for me currently since I upgraded RAM and have the suspicion that something isn't right with the RAM (more segfaulting processes and kernel panics than it's healthy). I tried Proper way to run memtest from heads? #535 (comment) however that leaves also only an unchanged screen after kexec.

[tlaurion]

@akunterkontrolle are you saying that the behavior changes with NO_IGFX or not for the 3 problems you specified above?

Memtest doesnt work. That's the most pressing problem for me currently since I upgraded RAM and have the suspicion that something isn't right with the RAM (more segfaulting processes and kernel panics than it's healthy). I tried #535 (comment) however that leaves also only an unchanged screen after kexec.

Last time I tested this on x230 (NO_IGFX) with manual kexec call from command line as specified there, it worked, and was confirmed by another user in need. It doesn't on latest memtest+ version? Note that it was 64 grub version. Please replicate and report under that issue, reopening it if needed.

[srgrint]

* The normal Debian installers don't work. Only way to install is via live cd, however the installer than offered lacks severely in features and options.

I would also be grateful if you could provide more information about your setup - ie what type thinkpad, what heads version and whether you have customised the configuration of heads when building. Also what version of the debian installer you have used would be helpful.

I fairly regularly run the debian installer under Heads and haven't had any problems myself. I usually use installer in text mode, but the graphics mode seems to boot fine as well.

I just tried on both my x220 (which has NO_IGFX set) and t430 (which by default does /not/ have NO_IGFX set). Both seem to work fine.

I am currently using the installer image at - https://cdimage.debian.org/cdimage/bookworm_di_alpha2/amd64/iso-cd/debian-bookworm-DI-alpha2-amd64-netinst.iso

It would be helpful if you try the exact same version of the installer as I have used, so we can try and work out what is different between our setups.

[tlaurion]

It seems that the simple answer on what Debian bookworm works while earlier didn't is because i915 is included in initramfs as tested here #1285 (comment)