From: Phillip Susi <psusi@ubuntu.com>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
Linux PCI <linux-pci@vger.kernel.org>
Subject: Re: enabling aspm on ati radeon
Date: Fri, 24 May 2013 15:57:51 -0400 [thread overview]
Message-ID: <519FC63F.3060205@ubuntu.com> (raw)
In-Reply-To: <11045555.dLhhFPGoSV@vostro.rjw.lan>
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Hash: SHA1
According to the PCI express standard, the Link Capabilities register
lies at offset 0xC within the PCI Express root port capabilities
descriptor. lspci decoded this and shows Unknown ASPM support,
because its value is zero, and this is why the kernel did not enable
ASPM in the Link Control register. According to the Intel datasheets,
the offsets AC-AFh ( the structure itself starts at A0h ) are
reserved. So astonishingly it seems that Intel does not know about
the Link Capabilities register! On the other hand, the contents of
the register actually do seem to be mostly correct, despite what their
datasheet claims. The one thing wrong with it is that it claims no
ASPM support, despite Intel claiming that it is supported.
For reference, the Intel datasheet I have been referring to is
document 324642-003: 2nd Generation Intel® CoreTM Processor Family
Desktop, Intel® Pentium® Processor Family Desktop, and Intel® Celeron®
Processor Family Desktop Datasheet, Volume 2, table 2-8 on page 84.
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prev parent reply other threads:[~2013-05-24 19:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <519443A1.8050905@ubuntu.com>
2013-05-16 8:58 ` enabling aspm on ati radeon Rafael J. Wysocki
2013-05-16 16:42 ` Bjorn Helgaas
[not found] ` <5195596C.3000406@ubuntu.com>
2013-05-17 17:31 ` Bjorn Helgaas
2013-05-17 18:04 ` Phillip Susi
2013-05-17 19:52 ` Bjorn Helgaas
2013-05-17 20:10 ` Phillip Susi
2013-05-17 20:24 ` Bjorn Helgaas
2013-05-17 21:12 ` Phillip Susi
2013-05-17 21:28 ` Bjorn Helgaas
2013-05-17 23:36 ` Phillip Susi
2013-05-17 23:52 ` Bjorn Helgaas
2013-05-18 0:15 ` Phillip Susi
2013-05-18 0:40 ` Bjorn Helgaas
2013-05-18 1:20 ` Phillip Susi
2013-05-20 13:34 ` Bjorn Helgaas
2013-05-20 20:01 ` Rafael J. Wysocki
2013-05-21 13:31 ` Phillip Susi
2013-05-21 18:50 ` Sebastian
2013-05-24 19:57 ` Phillip Susi [this message]
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