linux-kernel - Re: [PATCH v3 4/8] pciehp: Don't disable the link permanently, during removal

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Date:	Mon, 6 Jan 2014 17:03:39 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Rajat Jain <rajatxjain@...il.com>
Cc:	Rajat Jain <rajatjain.linux@...il.com>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Yijing Wang <wangyijing@...wei.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Guenter Roeck <groeck@...iper.net>,
	Rajat Jain <rajatjain@...iper.net>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH v3 4/8] pciehp: Don't disable the link permanently, during removal

On Sun, Jan 5, 2014 at 10:53 AM, Rajat Jain <rajatxjain@...il.com> wrote:
> Hello Bjorn,
>
> Just checking on the fate of this patch set...
>
> On Tue, Dec 17, 2013 at 5:02 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>> [+cc yinghai@...nel.org (seems to be Yinghai's preferred email]
>>
>> On Tue, Dec 17, 2013 at 12:06:05PM -0800, Rajat Jain wrote:
>>> We need future link up events for hot-add, thus don't disable
>>> the link permanently during device removal. Also, remove the static
>>> functions that are now left unused.
>>
>> The changelog should mention that this reverts part of 2debd9289997 ("PCI:
>> pciehp: Disable/enable link during slot power off/on").
>
> Sure. Do you want me to submit another patch set (bumping up the
> version) with this change log, or you'd want to add this change log
> while merging?
>
>>
>> Yinghai, can you tell us whether this is an issue on your systems?
>
> As Yinghai confirms further down this thread, his issue was confirmed
> by Intel to be a bug in the repeater chip.
> ----------------------------------
> Yinghai writes:
>> According to HW guys and Intel, that should be bug of repeater.
>>
> ---------------------------------
>  I don't know about the details of his scenario, except that when the
> adapter was disabled the repeater kept on flapping the link up & down
> (and hence disabling the link solved the problem then). Yinghai
> couldn't test, but I believe with this patch even if we disable
> presence detect interrupt, the "adapter present / no present" messages
> would (rightly) convert to "Link Up / Link Down" messages (since the
> repeater keeps on flapping the link).
>
> Since it is a platform specific bug, I'm not sure what can be done to
> remove those messages except may be reduce the verbosity? If you'd
> like I could change all the INFO messages to DBG messages.

Even if it's a defect in a particular piece of hardware, I don't want
to regress on that hardware, even if the regression is just extra
messages that we didn't see before.

I think ideally we would add some sort of quirk for that hardware so
it works just as well as it does today.  I think extra messages will
lead to a bug reports from users.

Bjorn
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