linux-kernel - Re: [PATCH] pciehp: Disable/enable link during slot power off/on

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Message-ID: <20120127092622.6d8c2ae8@jbarnes-desktop>
Date:	Fri, 27 Jan 2012 09:26:22 -0800
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Yinghai Lu <yinghai.lu@...cle.com>
Cc:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pciehp: Disable/enable link during slot power off/on

On Fri, 02 Dec 2011 15:10:08 -0800
Yinghai Lu <yinghai.lu@...cle.com> wrote:

> 
> One system have repeater in system board to support gen2 hotplug.
> 
> Found when EM is removed from some slots, /var/log/message will be full of
> "card present/not present" warning.
> 
> It turns out root complex still try to train the link to repeater because
> repeater is not reset.
> 
> This patch will disable link to make repeater could reset properly.
> Also could kill AER during EM removal.
> 
> Recently when testing hotplug on one system under development, found if boot
> the system without EM, and later hotplug does not work with Linux.
> But other OS is ok.
> The root cause is that bios left link disabled when slot is empty,
> and other OS is playing link disable bit in link ctrl during power on/off.
> 
> So We could do the same thing to disable/enable link during power off/on.
> 
> Signed-off-by: Yinghai Lu <yinghai.lu@...cle.com>

Ok I had to massage that commit message quite a bit, please let me know
if it's still accurate.

The 100ms delay still needs to be clarified; if it's really necessary
maybe we could move the delays into a delayed work handler?

-- 
Jesse Barnes, Intel Open Source Technology Center

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