kern/162578: 9.0-RC2's regression in power management on VIA Samuel 2

[Oli Kron]

>Number:         162578
>Category:       kern
>Synopsis:       9.0-RC2's regression in power management on VIA Samuel 2
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Nov 15 09:50:08 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Oli Kron
>Release:        9.0-RC2
>Organization:
>Environment:
FreeBSD ephraim.local 9.0-RC2 FreeBSD 9.0-RC2 #1: Sun Nov 13 19:21:14 CET 2011     toor at ephraim.local:/usr/obj/usr/src/sys/LEXVIA  i386
>Description:
I have a few machines (mostly routers) with VIA Samuel 2.
FreeBSD 9.0-RC2 breaks power management on them.

8.2-RELEASE detects:

  CPU: VIA Samuel 2 (532.64-MHz 686-class CPU)
    Origin = "CentaurHauls"  Id = 0x673  Family = 6  Model = 7
    Stepping = 3
    Features=0x803035<FPU,DE,TSC,MSR,MTRR,PGE,MMX>

and sysctl dev.cpu.0 says:

  dev.cpu.0.%desc: ACPI CPU
  dev.cpu.0.%driver: cpu
  dev.cpu.0.%location: handle=\_PR_.CPU0
  dev.cpu.0.%pnpinfo: _HID=none _UID=0
  dev.cpu.0.%parent: acpi0
  dev.cpu.0.freq: 532
  dev.cpu.0.freq_levels: 532/-1 266/-1
  dev.cpu.0.cx_supported: C1/0 C2/90 C3/900
  dev.cpu.0.cx_lowest: C2
  dev.cpu.0.cx_usage: 0.45% 99.54% 0.00% last 783us

In 8.2 I can use dev.cpu.0.cx_lowest=C2 in /etc/sysctl.conf
and powerd runs fine switching between 532 and 266 MHz.

FreeBSD 9.0-RC2 detects:

  CPU: VIA Samuel 2 (532.65-MHz 686-class CPU)
    Origin = "CentaurHauls"  Id = 0x673  Family = 6  Model = 7
    Stepping = 3
    Features=0x803035<FPU,DE,TSC,MSR,MTRR,PGE,MMX>
    AMD Features=0x80000000<3DNow!>
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the only difference

and sysctl dev.cpu.0 is:

  dev.cpu.0.%desc: ACPI CPU
  dev.cpu.0.%driver: cpu
  dev.cpu.0.%location: handle=\_PR_.CPU0
  dev.cpu.0.%pnpinfo: _HID=none _UID=0
  dev.cpu.0.%parent: acpi0
  dev.cpu.0.cx_supported: C1/0
  dev.cpu.0.cx_lowest: C1
  dev.cpu.0.cx_usage: 100.00% last 208us

Of course, dev.cpu.0.cx_lowest=C2 is not available and powerd
cannot start - "powerd -v" fails:

  powerd: lookup freq: No such file or directory

>How-To-Repeat:
install 9.0-RC2 on VIA Samuel 2 and:
1. sysctl dev.cpu.0 to see available frequencies and Cx states
2. try start powerd
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: