Hi all !

I had some troubles with my screen (extreme low back-light blinking rate) and make some search.

I found the perfect tool ! intel-gpu-tools.
But it was really hard to find how to use it, register names are really close, but wrong.

For example :

I have a broadwell CPU,
on this web page : https://01.org/linuxgraphics/documentation/hardware-specification-prms
we can found the PDF for broadwell :
https://01.org/sites/default/files/documentation/intel-gfx-prm-osrc-bdw-vol02c-commandreference-registers_4.pdf (/!\ heavy PDF >20Mo)
On page 1389, it explains how is the SBLC_PWM_CTL2 register bit by bit, its address (C8254h).

Now, on the tool side, using this register name:
[root@localhost jybz]# intel_reg --verbose read SBLC_PWM_CTL2
Error: /usr/share/igt-gpu-tools/registers/common_display.txt:1: ('CPU_VGACNTRL', '0x00041000', '')
Error: /usr/share/igt-gpu-tools/registers/broadwell:1: common_display.txt
Warning: reading '/usr/share/igt-gpu-tools/registers/broadwell' failed. Using builtin register spec.

No results.

Using the address instead of the name:
[root@localhost jybz]# intel_reg --verbose read 0x000C8254
Error: /usr/share/igt-gpu-tools/registers/common_display.txt:1: ('CPU_VGACNTRL', '0x00041000', '')
Error: /usr/share/igt-gpu-tools/registers/broadwell:1: common_display.txt
Warning: reading '/usr/share/igt-gpu-tools/registers/broadwell' failed. Using builtin register spec.
                   BLC_PWM_PCH_CTL2 (0x000c8254): 0x0040000b (freq 64, cycle 11)
Well, it is called "BLC_PWR_PCH_CTL2", I spend so much time on internet to find the bit definitions of this register, but this register doesn't exist!

Well, there is some warning and errors.
I seek in this files :
[root@localhost jybz]# cat /usr/share/igt-gpu-tools/registers/common_display.txt | grep "SBLC"
[root@localhost jybz]# cat /usr/share/igt-gpu-tools/registers/common_display.txt | grep "c8254"
('BLC_PWM_PCH_CTL2', '0x000c8254', '')
No answer for any SBLC, but at the address, the BLC_PWM_PCH_CTL2 is defined, unfortunately, this register isn't defined in the intel documentation.
There are other registers with wrong names I guess, like SBLC_PWM_CTL1.

Cheers, Jybz