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

-----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:

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To me it sounds more appropriate to adopt subsys_initcall() for

all

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the

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PCI Host Bridge controllers rather than having them as loadable

modules...

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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.

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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.

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As I said, it's not really a choice we have to make in the source

code,

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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