[coreboot] Patch: support for the Lenovo Thinkpad W520

[Patrick Rudolph]

Hello Charlotte,

thanks for adding support for W520.

Am 06.11.2016 um 09:33 schrieb Charlotte Plusplus:
> Hello
>
> I am new to coreboot. I tried to run coreboot on my Thinkpad W520 to
> replace my Sandy Bridge CPU by a Ivy Bridge CPU, since several people
> reported it worked very well.
>
> Following their suggestions, I simply tried to flash a T520 image to
> save time. It didn't work at all. I was very angry I had wasted almost
> 2 days doing that. So I took the time to port coreboot to the Thinkpad
> W520 following the specs from
> http://kythuatphancung.vn/uploads/download/5165b_Wistron_Kendo-3_WS_-_10222-SA_-_ThinkPad_W520.pdf
> and explore the issues I had (black screen, no boot)
>
> First, please find the patch attached to add support to the Thinkpad
> W520 mainboard. This patch is based on the T520 mainboard as the W520
> is very close. However, it needed romstage additions for ram init (cf
> p103 of the pdf)
Please use git ( 
https://www.coreboot.org/Development_Guidelines#How_to_contribute ) and 
gerrit ( http://review.coreboot.org/#/q/status:open ) to upload your 
patch. This allows easy reviewing and commenting, including an automatic 
build for every change made.
>
> I can now boot with various combinations of population of the Dimm
> slots, with the 4 slots all working, and the Dimm correctly identified
> by memtest
>
> However, I can not use my normal 8Gb Dimm sticks. One of them work,
> but 2x8Gb does not work most of the time. I get errors in memtest when
> I am lucky to boot. The sticks are DDR3L 2133 (bus speed 1066 MHz) and
> they worked fine with the bios 1.36: I tested the sticks for over 24h
> with memtest86 7.1 just a week ago to check how hot my old CPU would
> get.
Please note that I didn't test anything beyond DDR3-800. Some people 
reported that DDR3-1866 is working.
Can you try to limit max frequency to DDR3-1333 or DDR3-1600 (using 
max_mem_clock_mhz) and tell if it's working ?
> After further investigation, if I run memtest86 7.1 on the bios 1.36,
> it shows the correct information and timings: tCL-tRCD-tRP-tRAS are
> 11-11-11-29, and the RAM is running at 1066MHz.
>
> If I run memtest86 on coreboot, it shows the RAM is running at 931MHz
> with timings 10-10-10-28. All this would be fine if it didn't cause
> errors on the memtest86! It looks like the SPD decoding is buggy, and
> instead of using the optimal configuration (11-11-11) coreboot picks
> the next one.
CL11 is optimal configuration for DDR3-2133, but not for DDR3-1866. The 
choosen CL value is correct.
>
> I would be happy to fix that but I don't know where to look. I
> correctly put max_mem_clock_mhz = 1066 in devicetree.cb so I don't
> understand. Can I hardcode timing settings? Is there any other place I
> should check for SPD issues?
No you can't hardcode timings.
Native raminit is done in 
coreboot/src/northbridge/intel/sandybridge/raminit.c
Please have a look at this file first. I don't think that there are SPD 
issues, but there might be issues with frequencies of + DDR3-1600.

>
> There are some other W520 specific issues. I will try to prepare a
> wiki page to explain them. The big ones are:
>   - the bottom plastic case is conductive: if you add a J100 header,
> you must trim the ends or you will have shorts and the computer will
> not boot
>   - if you flash with a raspberry pi, you do not need external power.
> the 3V from pin 17 are enough. WP and HOLD can be left floating if you
> want. But you must insert all the pins at once, otherwise the W25Q64
> may not respond (it is weird, I see no logical reason, but it works
> reliably)
>   - native graphics initialization gave me video artifacts in seabios.
> Using the VGA bios fixed that
>
> On https://www.coreboot.org/Board:lenovo/t520 I see issues:
>      yellow USB port isn't powered in power-off state.
>      DisplayPort only connected to Discrete GPU
>      TPM. At the moment there is only basic support inside coreboot...
>      Boot time issues ( keyboard rest timeout )
>      ultrabay hot plug (event missing?)
>      some power management states missing
>
> I am new to coreboot. I could try to add the missing power management
> states. But can I please ask for pointers and suggestions? What is
> missing? Is there any documentation?
Power management is done through ACPI.
You'd need to figure out which ACPI functions are used by your operating 
system and implement/fix them.
> Also, in romstage I am not sure of :
>          /* Disable unused devices (board specific) */
>          RCBA32(FD) = 0x1ee51fe3;
You can dump the value stock lenovo bios sets at boot using the 
inteltool, that ships in coreboot's utils folder.
>
> The W520 is a bit different from a t420 and I think it may not be the
> same. How do I compute this number?
>
> Also, can I please ask for some help on USBDEBUG? I have a FT232R
> cable and enabled CONFIG_USBDEBUG_DONGLE_FTDI_FT232H. But I receive
> nothing. Is it necessary to have a FT232H? I looked at the code and it
> does not seem very specific. Having debug information would be helpful
> to fix these ram issues.
I'm using BeagleBone Black for USBDEBUG. I cannot tell if FT232R is 
working, too.
Please note that you have to use the USB port that has USBDEBUG 
capabilities. Other USB ports do not work. There's no fix rule where to 
find it.
Some thinkpads have it on the back, some are on the side. Please use 
lspci to identifiy it first.
For more information have a look at the wiki ( 
https://www.coreboot.org/EHCI_Debug_Port )
Once you got USBDEBUG working, please provide a full raminit log. It may 
help to fix the remaining issue.

Regards,
Patrick
>
> Charlotte
>
>