[coreboot] GeodeLX RAM initialisation issue

Nathan Williams nathan at traverse.com.au
Fri Nov 27 10:05:47 CET 2009

Nathan Williams wrote:
> Marc Jones wrote:
>> On Tue, Nov 24, 2009 at 1:09 AM, Nathan Williams <nathan at traverse.com.au> wrote:
>>> Marc Jones wrote:
>>>> On Mon, Nov 23, 2009 at 12:27 AM, Nathan Williams
>>>> <nathan at traverse.com.au> wrote:
>>>>> I managed to get the commercial BIOS to boot on my board and diffed it with coreboot:
>>>>> http://coreboot.pastebin.com/m39b22c21
>>>>> The only differences I can see are related to interrupts, which shouldn't matter in relation to
>>>>> my RAM problems.
>>>>> I have also run a memtest86 with the commercial BIOS (from bootable CDROM) and as a payload in coreboot.
>>>>> The commercial BIOS didn't have any errors, but my coreboot did.  So the hardware can't be too bad.
>>>> That looks like just the southbridge cs5536 target. The memory
>>>> differences would be in the processor geodelx target. Can you send
>>>> those results?
>>>> Marc
>>> I did some new MSR dumps.
>>> Diff:
>>> ./msrtool -t geodelx -t cs5536 -d amd_ref_bios
>>> http://coreboot.pastebin.com/m5e487f87
>>> AMD NAS reference BIOS:
>>> ./msrtool -t geodelx -t cs5536 -l -s amd_ref_bios
>>> http://coreboot.pastebin.com/madc04ac
>>> My Coreboot:
>>> ./msrtool -t geodelx -t cs5536 -l -s nathan_bios
>>> http://coreboot.pastebin.com/m7f35d855
>>> The diffs I did today show some differences with GLCP_DELAY_CONTROLS.
>>> Last time I added some code to force it to match the commercial BIOS
>>> GLCP_DELAY_CONTROLS MSR, but it didn't seem to make any difference.
>>> I also tested all the SODIMMS I have here (about 10) with the commercial BIOS.
>>> Each time I did a msrtool diff to one I saved on disk.
>>> Most are 333MHz, but 2 are 400MHz.  There weren't any changes to the MSRs.
>>> Could there be an issue with the initialisation sequence that reading MSRs
>>> after booting won't show?  Also, quite a few MSRs aren't defined in geodelx.c yet.
>>> Are there any obvious ones that should be added in?
>> --- AMD NAS reference BIOS
>> +++ Nathan's coreboot v3
>> #
>> #
>> -0x4c00000f 0x83f1_00aa_5696_0404
>> +0x4c00000f 0x8271_005a_ 5696_ 0404
>> It looks like coreboot and the ref bios detect different dimm
>> configuration. This timing setup could be part of the instability (I
>> don't think it explains the reset problem). Look at the code here:
>> SetDelayControl(void) and anywhere else that GLCP_DELAY_CONTROLS gets
>> set to see what might be happening. Make sure that MTest is disabled
>> in the ref bios setup. This setting is based on the number of devices
>> (load) there is on the dimm.
>> I didn't realize that so few registers were in the msr tool for
>> geodelx. You should add these:
>> 20000018h R/W Refresh and SDRAM Program (MC_CF07_DATA)
>> 10071007_00000040h Page 227
>> 20000019h R/W Timing and Mode Program (MC_CF8F_DATA) 18000008_287337A3h Page 229
>> 2000001Ah R/W Feature Enables (MC_CF1017_DATA) 00000000_11080001h Page 231
>> 2000001Bh RO Performance Counters (MC_CFPERF_CNT1) 00000000_00000000h Page 232
>> 2000001Ch R/W Counter and CAS Control (MC_PERCNT2) 00000000_00FF00FFh Page 233
>> 2000001Dh R/W Clocking and Debug (MC_CFCLK_DBUG) 00000000_00001300h Page 233
>> 4C00000Fh R/W GLCP I/O Delay
>> Controls(GLCP_DELAY_CONTROLS)00000000_00000000h Page 549
>> 4C000014h R/W GLCP System Reset and PLL Control (GLCP_SYS_RSTPLL)
>> Bootstrap specific Page 554
>> Marc
> I've now added the MSRs and uploaded to pastebin:
> http://coreboot.pastebin.com/m53aed60b
> My coreboot:
> http://coreboot.pastebin.com/md23bc6a
> ./msrtool -d AMD_NAS:
> http://coreboot.pastebin.com/m77663de5
> Tomorrow I'll try the tests on the NAS hardware, instead of our own motherboards
> just in case there are some hidden hardware issues.
> Regards,
> Nathan

On the NAS reference board I got the following diff between coreboot
and the commercial BIOS:


As you can see there are a lot of latency differences.
Unfortunately it was only later that I realised that the differences are because the bootstraps are set to bypass, which means coreboot uses 266 as the speed, where as the commercial bios uses 333.  So when I repeat the same on our boards, the only difference in the geodelx MSRs is:

-0x2000001d 0x0000000000000000
+0x2000001d 0x0000000000001000
-0: Tri-stating enabled
+1: Tri-stating disabled


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