Re: Linux 3.2.5

From: Matthias Schniedermeyer
Date: Tue Feb 07 2012 - 11:54:32 EST

On 07.02.2012 08:29, Linus Torvalds wrote:
> [ Matthew wasn't cc'd for this thread - see lkml or ask me or Greg to
> forward you the relevant emails ]
> On Tue, Feb 7, 2012 at 4:28 AM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote:
> >
> > According to your logs, 3.2.4 didn't touch device 5:0, while 3.2.5 does
> > disable ASPM.  (Are there any other messages regarding 0000:05:00.0?)
> Actually, if I read things right, I think 3.2.4 did touch the device
> too, just without the message.
> One of the things that the aspm patch does is to remove the code that used to do
> - if (aspm_clear_state)
> - return -EINVAL;
> in pcie_aspm_sanity_check(). So what I think happened for Matthias in
> 3.2.4 is that "pcie_aspm_sanity_check()" *always* failed (silently).
> Which caused us to disable ASPM for *every* device, and not even talk
> about it.
> With the new patch in place, 3.2.5 gets past that check, and
> pcie_aspm_sanity_check() now fails (with the message) for *some*
> devices. Which then causes us to disable ASPM for *those* devices, but
> not others. And that just sounds insane. It's sounds very broken for
> this situation, because the BIOS had apparently enabled ASPM for the
> PCIe bridge and the soubdblaster device, but then the "sanity check"
> disabled ASPM for the bridge (and presumably left it on for the
> soubdblaster).
> Resulting in a broken system - aspm on the device, but not the bridge
> leading up to it. Which I do not think is a correct situation.
> So aspm=force fixes the issue because it forces aspm for everything -
> which is fine. And 3.2.4 worked, because it *cleared* aspm for
> everything. But 3.2.5 (and presumably current -git) does not work,
> presumably because it clears ASPM randomly for bridge devices, while
> leaving it on for the devices they bridge to.
> Quite frankly, I think the pcie_aspm_sanity_check() logic is
> fundamentally broken. It's broken because it violates the whole point
> of the new model: it touches ASPM state for devices that firmware has
> set up, and it shouldn't touch it for!
> (It's also broken because it fundamentally makes the aspm disable be
> "per device", which seems totally wrong - aspm is a system issue, you
> can't just willy-nilly randomly enable it for one device without
> taking other devices into account).
> So I suspect the whole pcie_aspm_sanity_check() function should go away.
> Matthias - can you try to trivially just make pcie_aspm_sanity_check()
> always return 0 - remove the contents of that function, and just
> replace them all with just a simple "return 0;". Does that make things
> work for you?

So 3.2.5 with the following patch and without pcie_aspm=force:

- snip -
--- drivers/pci/pcie/aspm.c.orig 2012-02-07 15:17:05.068401852 +0100
+++ drivers/pci/pcie/aspm.c 2012-02-07 17:47:27.304684977 +0100
@@ -500,6 +500,8 @@
int pos;
u32 reg32;

+ return 0;
* Some functions in a slot might not all be PCIe functions,
* very strange. Disable ASPM for the whole slot
- snip -

Sound works. :-)

dmesg | grep -i aspm
[ 0.762726] ACPI FADT declares the system doesn't support PCIe ASPM, so disable it
[ 0.792913] ACPI _OSC control for PCIe not granted, disabling ASPM
[ 1.627719] e1000e 0000:03:00.0: Disabling ASPM L1

Bis denn

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