Bug 11329 - Incorrect value in /sys/devices/platform/w83627hf.656/cpu0_vid
Summary: Incorrect value in /sys/devices/platform/w83627hf.656/cpu0_vid
Alias: None
Product: Drivers
Classification: Unclassified
Component: Hardware Monitoring (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: Jean Delvare
Depends on:
Blocks: Regressions-2.6.26
  Show dependency tree
Reported: 2008-08-14 02:58 UTC by Jean-Luc Coulon
Modified: 2008-08-15 12:16 UTC (History)
2 users (show)

See Also:
Kernel Version: 2.6.27-rc3
Regression: Yes
Bisected commit-id:

output of cpuid command (3.55 KB, text/plain)
2008-08-14 04:31 UTC, Jean-Luc Coulon
/prot/cpuinfo (1.32 KB, text/plain)
2008-08-14 04:32 UTC, Jean-Luc Coulon
output of lspci -vv (16.83 KB, text/plain)
2008-08-14 04:43 UTC, Jean-Luc Coulon
isadump -y -k 0x87,0x87 0x2e 0x2f 7 (900 bytes, text/plain)
2008-08-14 07:37 UTC, Jean-Luc Coulon
Fix AMD K8 VID decoding (1.45 KB, patch)
2008-08-14 09:47 UTC, Jean Delvare
Details | Diff
Fix AMD K8 VID decoding (v2) (2.25 KB, patch)
2008-08-14 10:59 UTC, Jean Delvare
Details | Diff
Fix AMD K8 VID decoding (v3) (4.07 KB, patch)
2008-08-15 01:54 UTC, Jean Delvare
Details | Diff

Description Jean-Luc Coulon 2008-08-14 02:58:20 UTC
Latest working kernel version: 2.6.27-rc2-git1
Earliest failing kernel version: 2.6.27-rc2-git2
Distribution: Debian Sid
Hardware Environment: Athlon 64 x2 4200+
Software Environment: X86_64
Problem Description: in git1 and previous, cpu0_vid is reported as 1475 (which is correct). Since git2, it is reported as 725

Steps to reproduce: see in /sys/devices/platform/w83627hf.656/cpu0_vid

According to this value, the sensors command reports ccpu0_vid as +0.725V

This problem occurs in rc2-git2 and was not present in rc2-git1, it is still present in rc3-git1


Comment 1 Jean Delvare 2008-08-14 03:50:28 UTC
Thanks for reporting. This must be a side effect of that change:

The change added support for 6-bit VID codes for the AMD. Apparently in your case it broke the support for 5-bit VID codes as a side effect.

Please attach the contents of /proc/cpuid.

What exact Super-I/O chip model does your motherboard have? /sys/devices/platform/w83627hf.656/name should tell.
Comment 2 Jean-Luc Coulon 2008-08-14 04:31:33 UTC
Created attachment 17239 [details]
output of cpuid command
Comment 3 Jean-Luc Coulon 2008-08-14 04:32:23 UTC
Created attachment 17240 [details]
Comment 4 Jean-Luc Coulon 2008-08-14 04:43:59 UTC
Created attachment 17241 [details]
output of lspci -vv

The chipset is VIA K8T800pro
The host brisge is a VT8237

Comment 5 Jean Delvare 2008-08-14 04:50:18 UTC
The north and south bridges don't matter much here. What I need to know is the Super-I/O model. The w83627hf driver should tell you when you load it, and you can also read the name from /sys/devices/platform/w83627hf.656/name.
Comment 6 Jean-Luc Coulon 2008-08-14 05:53:41 UTC

This is w83627thf
Comment 7 Jean Delvare 2008-08-14 07:33:11 UTC
The W83627THF is a bit special, as it doesn't have dedicated VID inputs. The driver assumes that pins GP50 to GP56 are used as VID inputs, because that's what the demo circuit has in the datasheet, and several boards actually use this wiring. However, this is only a guess, and it might not work properly on all boards. This is fragile too, which might explain why a change in the handling of the AMD VID values has broken support of your motherboard.

To go on with the investigation, I need to know the value of a few register values. Please provide the output of the following command:

isadump -y -k 0x87,0x87 0x2e 0x2f 7

If it returns only 0xffs, please try instead:

isadump -y -k 0x87,0x87 0x4e 0x4f 7
Comment 8 Jean-Luc Coulon 2008-08-14 07:37:16 UTC
Created attachment 17242 [details]
isadump -y -k 0x87,0x87 0x2e 0x2f 7 

Output of isadump -y -k 0x87,0x87 0x2e 0x2f 7 is attached

Comment 9 Jean Delvare 2008-08-14 09:47:09 UTC
Created attachment 17246 [details]
Fix AMD K8 VID decoding

Can you please test this patch?
Comment 10 Jean-Luc Coulon 2008-08-14 10:41:32 UTC
Tested, it doesnt fiw the problem.

Comment 11 Jean Delvare 2008-08-14 10:59:14 UTC
Created attachment 17248 [details]
Fix AMD K8 VID decoding (v2)

I had forgotten one change. Please try this second patch.
Comment 12 Jean-Luc Coulon 2008-08-14 11:28:12 UTC
It works for me [tm]

Comment 13 Adrian Bunk 2008-08-14 12:46:07 UTC
Handled-By      : Jean Delvare <khali@linux-fr.org>
Patch           : http://bugzilla.kernel.org/attachment.cgi?id=17248
Comment 14 Jean Delvare 2008-08-15 01:54:57 UTC
Created attachment 17260 [details]
Fix AMD K8 VID decoding (v3)

Updated patch with additional technical documentation references.
Comment 15 Adrian Bunk 2008-08-15 12:16:39 UTC
fixed by commit cebd7709d396b59ff53b95fa3c4d9febbd4c010f

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