coreboot

http://imgur.com/a/o0CW3

I think the C native graphic init for ivy bridge on LVDS output is flawed. An easy fix would be to use libgfxinit, something like https://review.coreboot.org/#/c/19412/ should work on t520.

I guess the wrong code path is selected for your case (Ivy Bridge processor paired with Cougar Point PCH) in src/northbridge/intel/sandybridge/gma_sandybridge_lvds.c where it says:

    if ((bridge_silicon_revision() & BASE_REV_MASK) == BASE_REV_IVB) {
            return i915lightup_ivy(info, physbase, piobase, mmio, lfb);
    }

This decision should be made by PCH and not by processor, I guess. You can try it with the above lines removed.

Nico Huber wrote:

I guess the wrong code path is selected for your case (Ivy Bridge processor paired with Cougar Point PCH) in src/northbridge/intel/sandybridge/gma_sandybridge_lvds.c where it says:

    if ((bridge_silicon_revision() & BASE_REV_MASK) == BASE_REV_IVB) {
            return i915lightup_ivy(info, physbase, piobase, mmio, lfb);
    }

This decision should be made by PCH and not by processor, I guess. You can try it with the above lines removed.

I did another build with the lines removed, and got this result:

http://imgur.com/a/C7Kme

After the wave of light finishes washing over the screen and fades out the machine just reboots.

Hmmm, looks like I guessed wrong. The code is possibly more broken than I thought. So your best option is to use libgfxinit, like Arthur said. Since it's written in Ada, you'd probably have to rebuild your coreboot toolchain with GNAT installed. Just install gnat (package sometimes called gcc-ada) in the same version as gcc, run make crossgcc-clean and make crossgcc-i386. Then apply the same changes as done in https://review.coreboot.org/#/c/19412/ for the X230 to the T520 and select "Use libgfxinit..." below the native gfx init (NGI) option. Just tell us if you need help with the patching.

Btw. Windows is currently not supported along with NGI. It needs additional help by a so called Video BIOS Table (VBT). Work to add that VBT to coreboot in a cross-platform way is in progress.

Nico Huber wrote:

Hmmm, looks like I guessed wrong. The code is possibly more broken than I thought. So your best option is to use libgfxinit, like Arthur said. Since it's written in Ada, you'd probably have to rebuild your coreboot toolchain with GNAT installed. Just install gnat (package sometimes called gcc-ada) in the same version as gcc, run make crossgcc-clean and make crossgcc-i386. Then apply the same changes as done in https://review.coreboot.org/#/c/19412/ for the X230 to the T520 and select "Use libgfxinit..." below the native gfx init (NGI) option. Just tell us if you need help with the patching.

Btw. Windows is currently not supported along with NGI. It needs additional help by a so called Video BIOS Table (VBT). Work to add that VBT to coreboot in a cross-platform way is in progress.

I made those changes and built coreboot with libgfxinit. The result is no power on display (not just a blank screen, the backlight never turns on at all). I tried with both VGA text mode and linear framebuffer under the display settings.

Could it be that libgfxinit is not compatible with my display panel? It is B156HW01 V.7.

It's unlikely that the panel is incompatible. Though if both code paths fail, maybe there is a problem with its EDID.

Please attach your .config, src/mainboard/lenovo/t520/gma-mainboard.ad* and, if possible, a coreboot log taken with CONFIG_DEBUG_ADA_CODE=y and loglevel >= Debug.