linux-kernel - Re: [PATCH V5 1/3] pci: Add PCIe driver for Samsung Exynos

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Date:	Fri, 14 Jun 2013 12:53:11 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Jingoo Han <jg1.han@...sung.com>
Cc:	'Arnd Bergmann' <arnd@...db.de>,
	'Jason Gunthorpe' <jgunthorpe@...idianresearch.com>,
	linux-samsung-soc@...r.kernel.org,
	'Siva Reddy Kallam' <siva.kallam@...sung.com>,
	'Surendranath Gurivireddy Balla' <suren.reddy@...sung.com>,
	linux-pci@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, 'Kukjin Kim' <kgene.kim@...sung.com>,
	'Bjorn Helgaas' <bhelgaas@...gle.com>,
	'Andrew Murray' <andrew.murray@....com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V5 1/3] pci: Add PCIe driver for Samsung Exynos

On Fri, Jun 14, 2013 at 05:18:46PM +0900, Jingoo Han wrote:
> On Thursday, June 13, 2013 11:14 PM, Arnd Bergmann wrote:
> > On Thursday 13 June 2013 22:22:31 Jingoo Han wrote:
[...]
> > > +static int __exit exynos_pcie_remove(struct platform_device *pdev)
> > > +{
> > > +	struct pcie_port *pp = platform_get_drvdata(pdev);
> > > +
> > > +	clk_disable_unprepare(pp->bus_clk);
> > > +	clk_disable_unprepare(pp->clk);
> > > +
> > > +	return 0;
> > > +}
> > 
> > You also don't remove the PCI devices here, as mentioned in an earlier
> > review.
> 
> I reviewed Marvell PCIe driver and Tegra PCIe driver; however,
> I cannot know what you mean.
> 
> Could let me know which additional functions are needed?

We don't currently do that on Tegra either. pci-mvebu doesn't do that
either, but they don't implement the driver's .remove() in the first
place.

I think the biggest missing piece is pci_common_exit(), the counterpart
of pci_common_init(), to cleanup a host bridge on ARM. I haven't looked
in detail at the other architectures, but I suspect there must be some
code to call when a host bridge is removed.

Looking at drivers/pci/remove.c, it seems like pci_remove_root_bus()
might be what we're looking at. It isn't exported so it can't be used by
modules, but that can be changed. Is that how a host bridge is typically
removed from the system?

Thierry

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