linux-kernel - RE: [PATCH v10 4/6] PCI: hisi: Add PCIe host support for HiSilicon SoC Hip05

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Message-ID: <EE11001F9E5DDD47B7634E2F8A612F2E162436BC@lhreml503-mbs>
Date:	Wed, 14 Oct 2015 09:56:09 +0000
From:	Gabriele Paoloni <gabriele.paoloni@...wei.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	"Wangzhou (B)" <wangzhou1@...ilicon.com>,
	Bjorn Helgaas <helgaas@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"jingoohan1@...il.com" <jingoohan1@...il.com>,
	"pratyush.anand@...il.com" <pratyush.anand@...il.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"thomas.petazzoni@...e-electrons.com" 
	<thomas.petazzoni@...e-electrons.com>,
	"lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
	"james.morse@....com" <james.morse@....com>,
	"Liviu.Dudau@....com" <Liviu.Dudau@....com>,
	"jason@...edaemon.net" <jason@...edaemon.net>,
	"robh@...nel.org" <robh@...nel.org>,
	"gabriel.fernandez@...aro.org" <gabriel.fernandez@...aro.org>,
	"Minghuan.Lian@...escale.com" <Minghuan.Lian@...escale.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	zhangjukuo <zhangjukuo@...we.i.com>,
	qiuzhenfa <qiuzhenfa@...ilicon.com>,
	"liudongdong (C)" <liudongdong3@...wei.com>,
	qiujiang <qiujiang@...wei.com>,
	"xuwei (O)" <xuwei5@...ilicon.com>,
	"Liguozhu (Kenneth)" <liguozhu@...ilicon.com>,
	"Wangkefeng (Kevin)" <wangkefeng.wang@...wei.com>,
	Rob Herring <robh+dt@...nel.org>
Subject: RE: [PATCH v10 4/6] PCI: hisi: Add PCIe host support for HiSilicon
 SoC Hip05



> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd@...db.de]
> Sent: Wednesday, October 14, 2015 10:42 AM
> To: Gabriele Paoloni
> Cc: Wangzhou (B); Bjorn Helgaas; Bjorn Helgaas; jingoohan1@...il.com;
> pratyush.anand@...il.com; linux@....linux.org.uk;
> thomas.petazzoni@...e-electrons.com; lorenzo.pieralisi@....com;
> james.morse@....com; Liviu.Dudau@....com; jason@...edaemon.net;
> robh@...nel.org; gabriel.fernandez@...aro.org;
> Minghuan.Lian@...escale.com; linux-pci@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; devicetree@...r.kernel.org; linux-
> kernel@...r.kernel.org; zhangjukuo; qiuzhenfa; liudongdong (C);
> qiujiang; xuwei (O); Liguozhu (Kenneth); Wangkefeng (Kevin); Rob
> Herring
> Subject: Re: [PATCH v10 4/6] PCI: hisi: Add PCIe host support for
> HiSilicon SoC Hip05
> 
> On Wednesday 14 October 2015 09:31:48 Gabriele Paoloni wrote:
> > >
> > > > To me it sounds more appropriate to adopt subsys_initcall() for
> all
> > > the
> > > > PCI Host Bridge controllers rather than having them as loadable
> > > modules...
> > > >
> > > > What is your view?
> > >
> > > subsys_initcall() sounds odd because it's a driver rather than a
> > > subsystem,
> > > but I realize that most of the other levels don't fit any better.
> >
> > Yes well I was seeing for example the vgaarb
> > http://lxr.free-electrons.com/source/drivers/gpu/vga/vgaarb.c#L1357
> >
> > That in the init is calling pci_get_subsys()
> >
> > So I was wondering that the PCI devices may not be registered unless
> > we also init the PCI host bridge through subsys_initcall()...
> 
> I think this should work as is: the code first looks for devices
> that are already there and then registers a notifier for devices
> that show up later. This is meant to work for both devices that
> are hotplugged at a later point as well as PCI buses that are
> already there but not yet probed.
> 
> > But then maybe is the vgaarb to be buggy...
> 
> Possible. It may well be that the code is only tested on x86,
> which always probes its PCI very early.
> 
> > > As I said, it's not really a choice we have to make in the source
> code,
> > > we can use subsys_initcall together with module_exit(), or we can
> > > create a helper macro that is similar to module_platform_driver()
> > > specifically for PCI that uses a particular initcall level.
> >
> > Ok got it. But I guess this needs to be thought and applied to all
> > the PCI host bridge controllers...
> >
> > So maybe for this driver I can use module_platform_driver_probe()
> > and then we can see...
> 
> Sounds good. Let's focus on getting the driver merged first and
> then follow up with a patch to get this right for all PCI hosts.

Ok good let's do like this then

will change in v11

Again Many Thanks

Gab

> 
> 	Arnd
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