Bug 2974

Summary:	PBLK length 7 considered invalid
Product:	ACPI	Reporter:	Herman Sheremetyev (herman)
Component:	Power-Processor	Assignee:	acpi_power-processor
Status:	REJECTED DUPLICATE
Severity:	normal	CC:	acpi-bugzilla
Priority:	P2
Hardware:	i386
OS:	Linux
Kernel Version:	2.6.7	Subsystem:
Regression:	---	Bisected commit-id:
Attachments:	allows PBLK length of 7 in addition to 6 to be acceptable disassembled DSDT from BIOS v0209A for Asus M6N

Description Herman Sheremetyev 2004-06-28 10:02:13 UTC

Distribution:  Fedora Core 2
Hardware Environment: Asus M6N series notebook, Pentium-M 1600Mhz
Software Environment: Linux
Problem Description: the BIOS provides a PBLK length of 7 which is considered
invalid by the current Linux ACPI implementation and causes C2 processor state
to be unsupported.  It seems that 7 should be an acceptable value as Intel
shipped docs and chipsets with PBLK of length 7 in the past (maybe still do?).

Steps to reproduce: cat /proc/acpi/processor/CPU1/power

Comment 1 Herman Sheremetyev 2004-06-28 10:04:11 UTC

Created attachment 3269 [details]
allows PBLK length of 7 in addition to 6 to be acceptable

Comment 2 Luming Yu 2004-06-28 18:53:12 UTC

  ACPI spec 2.0b 16.2.3.3.1.17 constrains the possible value of PBKLen.
It should be either 0 or 6. So, I don't like the patch.

Comment 3 Zhu Yi 2004-06-28 19:39:43 UTC

AFAIK, there are a number of laptops have PBLKLen other than 6, like 5, 7, etc.
In most cases, using the BIOS PBLKLen to request_region won't crash us. May I 
suggest to check "PBLKLen != 6" only when acpi=strict? On other conditions, we 
may permit more values like 5, 7 to walk around the ACPI BIOS bug. 

BTW, What does Windows do on your system?

Comment 4 Herman Sheremetyev 2004-06-28 21:23:39 UTC

I just realized that the DSDT does contain a _CST method with C2 and C3 defined,
and if I understand it correctly they override the PBLK registers, so maybe 7
was meant to disable PBLK in this case after all...I guess that would also
explain why C3_Latency is set to 1001 in the FADT.  The "_CST patch" is probably
the right solution to this problem rather than the one I propose, it's being
dealt with in this bug report:

http://bugzilla.kernel.org/show_bug.cgi?id=1958

As a result I'm going to close this bug report.



*** This bug has been marked as a duplicate of 1958 ***

Comment 5 Zhu Yi 2004-06-29 19:10:50 UTC

Can you please attach your DSDT?

Comment 6 Herman Sheremetyev 2004-06-30 07:54:56 UTC

Created attachment 3291 [details]
disassembled DSDT from BIOS v0209A for Asus M6N

Hi Zhu,

I'm attaching the disassembled DSDT from the latest BIOS version.  To answer
your earlier question, I don't actually run Windows so I'm not sure how it
behaves on this laptop with regard to C2/C3.

-Herman