linux-kernel - Re: [PATCH] ASPM: Fix pcie devices with non-pcie children

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Message-ID: <20120328211559.GA10511@burratino>
Date:	Wed, 28 Mar 2012 16:15:59 -0500
From:	Jonathan Nieder <jrnieder@...il.com>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	bhelgaas@...gle.com, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, stable@...r.kernel.org,
	Colin Ian King <colin.king@...onical.com>,
	janek <jan0x6c@...il.com>
Subject: Re: [PATCH] ASPM: Fix pcie devices with non-pcie children

Hi Matthew,

Matthew Garrett wrote:

> Commit 4949be16822e92a18ea0cc1616319926628092ee changed the behaviour of
> pcie_aspm_sanity_check() to always return 0 if aspm is disabled, in order
> to avoid cases where we changed ASPM state on pre-PCIe 1.1 devices. This
> skipped the secondary function of pcie_aspm_sanity_check which was to avoid
> us enabling ASPM on devices that had non-PCIe children, causing us to hit
> a BUG_ON later on. Move the aspm_disabled check so we continue to honour
> that scenario.

janek (cc-ed) never experienced the BUG_ON.  Instead, starting with
v3.3 and v3.2.12 his hard disk using the pata_jmicron driver was not
detected during boot-up, resulting in the message "gave up waiting for
root device" and a failed boot.

Found in

  Debian kernel 3.2.12-1
  Debian kernel 3.3-1~experimental.1
  Upstream 3.3
  Linus's "master" as of 2012-03-28

Based on the thread [1] we blamed 4949be16822.  janek tried the patch
above on top of linus's "master".  The result:

> Thanks. This patch fixes the problem.

In other words, this gets the pata_jmicron driver to enumerate its
drives again, a positive effect that wasn't even advertised in the
commit message. ;-)  Thanks for writing it.

Sincerely,
Jonathan

[1] http://thread.gmane.org/gmane.linux.kernel/1271264/focus=1271785
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