netdev - RE: pcie_get_minimum_link returns 0 width

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Date:	Mon, 26 Aug 2013 23:36:50 +0000
From:	"Yuval Mintz" <yuvalmin@...adcom.com>
To:	"Bjorn Helgaas" <bhelgaas@...gle.com>
cc:	"jacob.e.keller@...el.com" <jacob.e.keller@...el.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: pcie_get_minimum_link returns 0 width

> > Hi,
> >
> > I tried adding support for the newly added 'pcie_get_minimum_link' into
> the
> > bnx2x driver, but found out the some of my devices started showing width
> x0.
> >
> > By adding debug prints, I've found out there were devices up the chain that
> > Showed 0 when their PCI_EXP_LNKSTA was read by said function.
> > However, when I tried looking via lspci the output claimed the width was
> x4.
> 
> I don't see a 'pcie_get_minimum_link()' function in my current tree
> (git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git "next"
> branch).  Maybe seeing your patch (with the debug prints) would give
> me a hook for somewhere to start looking.

You've acked the patch and it was applied in net-next; Obviously it has yet
to migrate to your tree. 

> 
> Can you figure out why lspci shows the correct value and this kernel
> interface does not?  The current lspci source is in
> git://git.kernel.org/pub/scm/utils/pciutils/pciutils.git and the
> relevant code is probably in cap_express_link() here:
> http://git.kernel.org/cgit/utils/pciutils/pciutils.git/tree/ls-caps.c#n750

Traced the read as going via the pci-sysfs. Where should I look for the bus's
read ops?

Thanks,
Yuval

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