linux-kernel - Re: [RFC 2/4] PCI: generic: Add support for ARM64 and MSI(x)

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Message-ID: <20140930120344.GA14215@e102568-lin.cambridge.arm.com>
Date:	Tue, 30 Sep 2014 13:03:44 +0100
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	Will Deacon <Will.Deacon@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"jason@...edaemon.net" <jason@...edaemon.net>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [RFC 2/4] PCI: generic: Add support for ARM64 and MSI(x)

On Mon, Sep 29, 2014 at 03:36:30PM +0100, Arnd Bergmann wrote:
> On Sunday 28 September 2014 15:53:28 suravee.suthikulpanit@....com wrote:
> > +
> > +#ifdef CONFIG_ARM64
> > +struct pci_bus *gen_scan_root_bus(struct device *parent, int bus,
> > +                                      struct pci_ops *ops, void *sysdata,
> > +                                      struct list_head *resources)
> > +{
> 
> I don't see anything ARM64 specific in this, the function only uses
> the newly added generic helpers.

I do not see it either, it is just a copy'n'paste of common PCI code,
plus msi management.

> >  static int gen_pci_probe(struct platform_device *pdev)
> >  {
> > @@ -326,6 +385,7 @@ static int gen_pci_probe(struct platform_device *pdev)
> >         struct device *dev = &pdev->dev;
> >         struct device_node *np = dev->of_node;
> >         struct gen_pci *pci = devm_kzalloc(dev, sizeof(*pci), GFP_KERNEL);
> > +#ifndef CONFIG_ARM64
> >         struct hw_pci hw = {
> >                 .nr_controllers = 1,
> >                 .private_data   = (void **)&pci,
> > @@ -333,6 +393,7 @@ static int gen_pci_probe(struct platform_device *pdev)
> >                 .map_irq        = of_irq_parse_and_map_pci,
> >                 .ops            = &gen_pci_ops,
> >         };
> > +#endif
> >  
> 
> Same here, I'd suggest marking this "#ifdef CONFIG_ARM" instead, as hw_pci
> is an arm32 specific data structure.

I do not think we need hw struct at all, see below, we can write code so
that we do not rely on ARM32 PCI bios, I will have a stab at that and
post the resulting code.

> >         if (!pci)
> >                 return -ENOMEM;
> > @@ -368,8 +429,24 @@ static int gen_pci_probe(struct platform_device *pdev)
> >                 gen_pci_release_of_pci_ranges(pci);
> >                 return err;
> >         }
> > +#ifdef CONFIG_ARM64
> >  
> > +#ifdef CONFIG_PCI_MSI
> > +       pci->msi_parent = of_parse_phandle(np, "msi-parent", 0);
> > +       if (!pci->msi_parent) {
> > +               dev_err(&pdev->dev, "Failed to allocate msi-parent.\n");
> > +               return -EINVAL;
> > +       }
> > +#endif
> 
> We probably want to enable MSI unconditionally on ARM64, so the #ifdef is
> not necessary here. However, I don't think that a missing msi-parent should
> be a fatal error here: we can still continue without MSI support if this
> case.
> 
> > +       if (!gen_scan_root_bus(&pdev->dev, pci->cfg.bus_range.start,
> > +                              &gen_pci_ops, pci, &pci->resources)) {
> > +               dev_err(&pdev->dev, "failed to enable PCIe ports\n");
> > +               return -ENODEV;
> > +       }
> > +#else
> >         pci_common_init_dev(dev, &hw);
> > +#endif /* CONFIG_ARM64 */
> > 
> 
> Again, just make the pci_common_init_dev() call #ifdef CONFIG_ARM, and move
> the generic case after it, outside of the #ifdef.

I went through the code quickly but I think we can (and should) remove
this quite ugly ifdeffery altogether. Most of the functionality in
pci_common_init_dev() can be implemented through the common PCI API (and this
would make this driver arch agnostic as it should be), I will go through ARM32
PCI bios code to check what is executed in detail in pci_common_init_dev() and
make sure that we follow those initialization steps in the resulting probe code
for this PCI generic host controller driver.

Lorenzo

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