old.md 10 KB
% Development notes (old/obsolete notes)
For current notes, see [](./).
These are old (obsolete) notes that mare kept because they might become useful again in the future.
Table of contents
X60 native graphics initialization (with backlight controls) {#x60_native_notes}
This is now obsolete. A better way was found (included in libreboot): http://review.coreboot.org/#/c/6731/
Also check #5320_kernel312fix (to fix 3D on kernel 3.12/higher)
The fix below was done on 5320/6 (from review.coreboot.org) but should work just fine on later versions of 5320.
Native gpu init + backlight controls! (Fn keys). Also confirmed on X60 Tablet (1024x768) and X60 Tablet (1400x1050)
Add backlight controls: in src/mainboard/lenovo/x60/devicetree.cb, change gpu_backlight to 0x879F879E
That's all! This has also been backported into libreboot 5th release (line 1233 in src/mainboard/lenovo/x60/i915io.c). GNUtoo (Denis Carikli) told me about the register BLC_PWM_CTL and that you could set it to control backlight. I read that address using devmem2 while running the VBIOS:
# devmem2 0xe4361254 w
The change is also included in libreboot 6.
When doing this, it gave back that value. The same trick was used to get backlight controls for T60 (see #t60_native_notes).
Further notes
Reading 0xe4361254 (address) in Lenovo BIOS always yields FFFFFFFF, even when writing to it (and writing to it doesn't affect brightness controls). 'mtjm' on IRC found that the buttons (Fn keys) control /sys/class/backlight/acpi_video0 which has no affect on 61254 (BLC_PWM_CTL). This person says intel_backlight has different values and uses the register. devmem2 works, needs checking lspci -vv for where the memory is mapped, which is different than on coreboot; mtjm found that it was 0xec061254 on his system (X60 Tablet), and the register value is different too. This is relevant, because we still don't know how backlight controls are actually handled. We got it working by accident. We need to know more..
Intel-gpu-tools may prove useful for further debugging: http://cgit.freedesktop.org/xorg/app/intel-gpu-tools/
mtjm says 0xe4300000 is an MMIO region of the gpu (lspci -vv shows it), 0x61254 (BLC_PWM_CTL) is a documented register. Searching the kernel driver for backlight shows that in intel_panel.c this register is used (there is an XXX comment about finding the right value, where recent kernels get it from.
What we want to do is calculate a good value, instead of setting it in devicetree.cb. mtjm says about backlight physics: it has a light source , uses pulse width modulation (PWM) to turn it on/off, dimming is done by spending less time on. Note: this may not be correct; this person says that their understanding is based on how the Lenote yeeloong works.
mtjm goes on to say, that the register specifies the frequency used for PWM in its depending on the GPU core frequency, so it might be possible to calculate it without hardcoded laptop-specific values. Therefore, I am supposed to find out the 'display core frequency' (mtjm says there might be a register for it; also, it might be in 5320 or the replay code) and the PWM modulation frequency. https://en.wikipedia.org/wiki/Backlight#Flicker_due_to_backlight_dimming
phcoder (Vladimir Serbinenko) who is author of 5320 (review.coreboot.org) talks about 'duty cycle limit' and 'flickering frequency'.
T60 native graphics initialization (with backlight controls) {#t60_native_notes}
This is now obsolete. A better way was found (included in libreboot): http://review.coreboot.org/#/c/6731/
Also check #5320_kernel312fix (to fix 3D on kernel 3.12/higher)
The fix below was done on an earlier version of 5345 changeset (review.coreboot.org), but should work on the current version. it is included in libreboot 6
Add backlight controls: in src/mainboard/lenovo/t60/devicetree.cb, change gpu_backlight to 0x58BF58BE
Hold on! Check ../misc/#get_edid_panelname to know what LCD panel you have. This is important for the next step!
Supported panels
See #lcd_i945_incompatibility.
i945: 3D fix (based on 5927) for kernel 3.12+ on 5320 {#5320_kernel312fix}
This is now obsolete. Merged in coreboot: http://review.coreboot.org/#/c/5927/
This needs to be rewritten (or better organized, or deleted?). This is also now included in libreboot 6 (using the proper way, not the 7c0000 method which was a hack)
This was done on 5320/6 so far. The fix below is for 5320/6 which is now obsolete. This needs to be re-done for the latest version of 5320. The fix below is (in practise) only for reference, therefore.
See #x60_cb5927_testing for the original (and current) fix, for the replay code. Now we want to implement that on top of http://review.coreboot.org/#/c/5320 which is the current code for native graphics initialization on i945.
src/northbridge/intel/i945/gma.c (using the 7c0000 hack) on 5320: 5320_7c0000_gma.c (rename it to gma.c, replacing the current one).
The above is a hack (as is the original). A better (more correct) method is implemented in later versions of 5927, so that should also be adapted for 5320. For now, you can use the above fix.
The correct way to do it is to set gtt address to (end of stolen memory
- gtt size), which is what later versions of 5927 do (successfully).
Here is some debugging output using intel_gpu_tools v1.2-1 (from apt-get repositories) using tool "intel_gtt":
- kernel 3.14.4:
- with libreboot 5th release (using the 7c0000 gtt hack from 5927/3): http://paste.debian.net/104306
- with coreboot+vgarom: http://paste.debian.net/104309
- kernel 3.2.0-60 (from apt-get repositories):
- with coreboot (no vbios or native init): http://paste.debian.net/104341
i945/X60: Coreboot 5927 testing (3D fix for kernel 3.12+ on replay code) {#x60_cb5927_testing}
This is now obsolete. Merged in coreboot: http://review.coreboot.org/#/c/5927/
The latest version as-is (5927/11) has not been tested by me yet. Always boot with 'drm.debug=0x06' kernel parameter when testing this.
This is the fix for 3D on kernel 3.12 and higher on i945 (ThinkPad X60 in this case). This is for the replay code. Libreboot 5th release has a version of this backported already (based on 5927/3 using the '7c0000' hack).
The replay code is obsolete (see 5320 changeset on review.coreboot.org for better version which supports more systems/screens, and then 5345 for T60). Information here for reference since that is where the fix was first applied.
Read the information on http://review.coreboot.org/#/c/5927/.
For historical purposes, here is a collection of IRC logs that once existed on this page, related to the issue: kernel312_irc.
PGETBL_CTL differs between VBIOS (-) and native graphics init (+).
- PGETBL_CTL: 0x3ffc0001\
- PGETBL_CTL: 0x3f800001
GTT (graphics translation table) size is PGETBL_save, max 256 KiB. BSM (Base of Stolen Memory) is given by the bios.
- 5927/7: 5927_7.tar.gz (GRUB graphics are correct now, and 3D still works)
- 5927/6: 5927_6.tar.gz (GRUB graphics still corrupt, 3D/everything still works after GRUB)
- 5927/5: 5927_5.tar.gz (GRUB graphics corrupt, 3D/everything still works after GRUB)
- 5927/3: 5927_3.tar.gz (3D still works! kernel 3.14.4) - the '7c0000' hack
- 5927/2: 5927_2.tar.gz (3D works! kernel 3.14.4) - the '7c0000' hack
- 5927/1 (didn't fix the 3D issue):
Copyright © 2014, 2015 Leah Rowe info@minifree.org\ Permission is granted to copy, distribute and/or modify this document under the terms of the Creative Commons Attribution-ShareAlike 4.0 International license or any later version published by Creative Commons; A copy of the license can be found at ../cc-by-sa-4.0.txt
Updated versions of the license (when available) can be found at https://creativecommons.org/licenses/by-sa/4.0/legalcode
UNLESS OTHERWISE SEPARATELY UNDERTAKEN BY THE LICENSOR, TO THE EXTENT POSSIBLE, THE LICENSOR OFFERS THE LICENSED MATERIAL AS-IS AND AS-AVAILABLE, AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE LICENSED MATERIAL, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHER. THIS INCLUDES, WITHOUT LIMITATION, WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT, ABSENCE OF LATENT OR OTHER DEFECTS, ACCURACY, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT KNOWN OR DISCOVERABLE. WHERE DISCLAIMERS OF WARRANTIES ARE NOT ALLOWED IN FULL OR IN PART, THIS DISCLAIMER MAY NOT APPLY TO YOU.
TO THE EXTENT POSSIBLE, IN NO EVENT WILL THE LICENSOR BE LIABLE TO YOU ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, NEGLIGENCE) OR OTHERWISE FOR ANY DIRECT, SPECIAL, INDIRECT, INCIDENTAL, CONSEQUENTIAL, PUNITIVE, EXEMPLARY, OR OTHER LOSSES, COSTS, EXPENSES, OR DAMAGES ARISING OUT OF THIS PUBLIC LICENSE OR USE OF THE LICENSED MATERIAL, EVEN IF THE LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH LOSSES, COSTS, EXPENSES, OR DAMAGES. WHERE A LIMITATION OF LIABILITY IS NOT ALLOWED IN FULL OR IN PART, THIS LIMITATION MAY NOT APPLY TO YOU.
The disclaimer of warranties and limitation of liability provided above shall be interpreted in a manner that, to the extent possible, most closely approximates an absolute disclaimer and waiver of all liability.