From: Bjorn Helgaas <helgaas@kernel.org>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Sinan Kaya <okaya@codeaurora.org>,
linux-pci@vger.kernel.org, Zhou Wang <wangzhou1@hisilicon.com>,
Phil Edworthy <phil.edworthy@renesas.com>,
Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [RFC] ARM/ARM64 PCI_PROBE_ONLY platforms
Date: Mon, 1 Feb 2016 15:19:36 -0600 [thread overview]
Message-ID: <20160201211936.GE4861@localhost> (raw)
In-Reply-To: <20160201162838.GB30869@red-moon>
On Mon, Feb 01, 2016 at 04:28:38PM +0000, Lorenzo Pieralisi wrote:
> On Fri, Jan 29, 2016 at 05:25:38PM -0600, Bjorn Helgaas wrote:
> > On Wed, Jan 20, 2016 at 06:10:03PM +0000, Lorenzo Pieralisi wrote:
> >
> > > To do that, we must claim resources on PCI_PROBE_ONLY systems, but
> > > I know for certain Bjorn does not like the idea (I let you trawl
> > > the archives - at least he does not accept the idea of claiming
> > > resources ONLY on PCI_PROBE_ONLY systems, he thinks we should
> > > always claim resources regardless of that flag and fall-back to
> > > reassigning them in case claiming fails. That's perfectly reasonable,
> > > at least on systems with FW initializing PCI). The problem is dealing
> > > with legacy, so switching to resources claiming by default is a tad
> > > complicated, at least for testing (code is easy to implement).
> >
> > I'd like to think of PCI_PROBE_ONLY basically as "setting
> > IORESOURCE_PCI_FIXED for every BAR", i.e., we can do everything we
> > normally do *except* write to the BAR (of course we have to write to
> > it to size the BAR during enumeration, but we have to restore the
> > original value).
>
> I am honestly a bit confused about the distinction between
> PCI_PROBE_ONLY and "IORESOURCE_PCI_FIXED for every BAR", the more
> so if I read the resources assignment code, in particular:
>
> pci_assign_resource()
>
> in drivers/pci/setup-res.c
>
> That function assigns the resource but does not update the BAR
> if IORESOURCE_PCI_FIXED is set. I wonder why the resource is
> assigned at all if IORESOURCE_PCI_FIXED is set, probably to
> initialize its parent pointer and set it, still, the value in
> the struct resource may differ from what's in the BAR, I am not sure
> I understand why we are happy with that or I am reading code the
> wrong way (does not this give a view of resource tree disconnected
> from how HW is actually programmed ?)
I'm not happy with that -- it's just one of our many problems.
The assignment code doesn't doesn't really pay attention to
IORESOURCE_PCI_FIXED. I don't think it pays attention to
PCI_PROBE_ONLY either, except that some arches don't even call the
assignment code if it is set.
Bjorn
next prev parent reply other threads:[~2016-02-01 21:19 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-20 16:04 [RFC] ARM/ARM64 PCI_PROBE_ONLY platforms Lorenzo Pieralisi
2016-01-20 16:13 ` Sinan Kaya
2016-01-20 18:10 ` Lorenzo Pieralisi
2016-01-20 18:15 ` Sinan Kaya
2016-01-29 23:26 ` Bjorn Helgaas
2016-01-22 16:28 ` Phil Edworthy
2016-01-25 17:51 ` Lorenzo Pieralisi
2016-01-28 17:27 ` Lorenzo Pieralisi
2016-01-29 12:02 ` Gabriele Paoloni
2016-01-29 6:32 ` Pratyush Anand
2016-01-29 23:25 ` Bjorn Helgaas
2016-02-01 16:28 ` Lorenzo Pieralisi
2016-02-01 21:19 ` Bjorn Helgaas [this message]
2016-01-29 23:06 ` Bjorn Helgaas
2016-01-30 0:14 ` Sinan Kaya
2016-01-30 13:30 ` Bjorn Helgaas
2016-01-30 17:51 ` Okaya
2016-02-01 15:25 ` Lorenzo Pieralisi
2016-02-01 21:12 ` Bjorn Helgaas
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