linux-kernel - Re: driver skip pci_set

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Message-ID: <53454660.5090603@pobox.com>
Date:	Wed, 09 Apr 2014 09:08:48 -0400
From:	Mark Lord <mlord@...ox.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>, Theodore Ts'o <tytso@....edu>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: driver skip pci_set_master, fix it? No.

On 14-04-08 10:51 PM, Benjamin Herrenschmidt wrote:
> On Tue, 2014-04-08 at 17:18 -0400, Mark Lord wrote:
>>> I assume you're talking about the one added by cf3e1feba7f9 ("PCI:
>>> Workaround missing pci_set_master in pci drivers"), but as far as I
>>> can tell, it only calls pci_set_master() for *bridge* devices.  What
>>> am I missing?  Is pci_set_master() being called for your endpoint?
>>> What path is that?
>>
>> Yes, it is being called during execution of the _probe() function in my driver,
>> as evidenced by the annoying (and wrong) message it produces.
>>
>> Next time I've got the hardware at hand, I'll put a "dump_stack()" into there
>> to see the exact calling path.
> 
> Note that one of the reason we want to do it early on bridges is that without it,
> we may also not get the PCIe error messages.

Sure, for bridges.

I'll get a stack trace later today, but what I suspect is happening
is that this multi-function card is being treated by the PCI layers
as a "bridge" for purposes of the multiple virtual functions it implements.

We will probably need to distinguish this kind of device from real bridges here.
-- 
Mark Lord
Real-Time Remedies Inc.
mlord@...ox.com
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