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

[Gabriele Paoloni]

> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd at arndb.de]
> Sent: Wednesday, October 14, 2015 10:42 AM
> To: Gabriele Paoloni
> Cc: Wangzhou (B); Bjorn Helgaas; Bjorn Helgaas; jingoohan1 at gmail.com;
> pratyush.anand at gmail.com; linux at arm.linux.org.uk;
> thomas.petazzoni at free-electrons.com; lorenzo.pieralisi at arm.com;
> james.morse at arm.com; Liviu.Dudau at arm.com; jason at lakedaemon.net;
> robh at kernel.org; gabriel.fernandez at linaro.org;
> Minghuan.Lian at freescale.com; linux-pci at vger.kernel.org; linux-arm-
> kernel at lists.infradead.org; devicetree at vger.kernel.org; linux-
> kernel at vger.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