linux-kernel - RE: [PATCH V2 5/5] Microblaze: Modifying microblaze PCI subsytem to support generic Xilinx AXI PCIe Host Bridge IP driver

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Date:	Thu, 4 Feb 2016 05:49:20 +0000
From:	Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
To:	Bjorn Helgaas <helgaas@...nel.org>
CC:	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	Michal Simek <michals@...inx.com>,
	"lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
	"paul.burton@...tec.com" <paul.burton@...tec.com>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"wangyijing@...wei.com" <wangyijing@...wei.com>,
	"robh@...nel.org" <robh@...nel.org>,
	"russell.joyce@...k.ac.uk" <russell.joyce@...k.ac.uk>,
	Soren Brinkmann <sorenb@...inx.com>,
	"jiang.liu@...ux.intel.com" <jiang.liu@...ux.intel.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"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>,
	Ravikiran Gummaluri <rgummal@...inx.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: RE: [PATCH V2 5/5] Microblaze: Modifying microblaze PCI subsytem to
 support  generic Xilinx  AXI PCIe Host Bridge IP driver

> Subject: Re: [PATCH V2 5/5] Microblaze: Modifying microblaze PCI subsytem
> to support generic Xilinx AXI PCIe Host Bridge IP driver
> 
> [+cc Ben for real this time]
> 
> On Wed, Feb 03, 2016 at 10:32:07AM -0600, Bjorn Helgaas wrote:
> > [+cc Ben, pcibios_get_phb_of_node() question]
> >
> > On Tue, Jan 12, 2016 at 11:06:13PM +0530, Bharat Kumar Gogada wrote:
> > > This patch does required modifications to microblaze PCI subsystem,
> > > to work with generic driver (drivers/pci/host/pcie-xilinx.c) on
> > > Microblaze and Zynq.
> > >
> > > Signed-off-by: Bharat Kumar Gogada <bharatku@...inx.com>
> > > Signed-off-by: Ravi Kiran Gummaluri <rgummal@...inx.com> ...
> >
> > >  resource_size_t pcibios_align_resource(void *data, const struct resource
> *res,
> > >  				resource_size_t size, resource_size_t align)  {
> > > -	struct pci_dev *dev = data;
> > >  	resource_size_t start = res->start;
> > >
> > > -	if (res->flags & IORESOURCE_IO) {
> > > -		if (skip_isa_ioresource_align(dev))
> > > -			return start;
> > > -		if (start & 0x300)
> > > -			start = (start + 0x3ff) & ~0x3ff;
> > > -	}
> > > -
> > >  	return start;
> >
> > "return res->start;" is sufficient; no need for a temporary variable.
> >
Agreed will address in next patch.
> > >  }
> > >  EXPORT_SYMBOL(pcibios_align_resource);
> > >
> > > +int pcibios_add_device(struct pci_dev *dev) {
> > > +	dev->irq = of_irq_parse_and_map_pci(dev, 0, 0);
> > > +
> > > +	return 0;
> > > +}
> > > +EXPORT_SYMBOL(pcibios_add_device);
> > > +
> > >  /*
> > >   * Reparent resource children of pr that conflict with res
> > >   * under res, and make res replace those children.
> > > @@ -1335,9 +1308,21 @@ static void
> > > pcibios_setup_phb_resources(struct pci_controller *hose,
> > >
> > >  struct device_node *pcibios_get_phb_of_node(struct pci_bus *bus)  {
> > > -	struct pci_controller *hose = bus->sysdata;
> > > +	struct device_node *np;
> > > +
> > > +	for_each_node_by_type(np, "pci") {
> > > +		const void *prop;
> > > +		unsigned int bus_min;
> > > +
> > > +		prop = of_get_property(np, "bus-range", NULL);
> > > +		if (!prop)
> > > +			continue;
> > > +		bus_min = be32_to_cpup(prop);
> > > +		if (bus->number == bus_min)
> > > +			return np;
> > > +	}
> > >
> > > -	return of_node_get(hose->dn);
> > > +	return NULL;
> >
> > Hmmm.  The old microblaze code ("return of_node_get(hose->dn);") is
> > basically the same as the mips and powerpc versions.  The new code is
> > basically the same as the x86 version.
> >
> > I like the generic weak version in drivers/pci/of.c because it doesn't
> > use any arch-specific data, and it looks like if we just set the
> > struct device.of_node members correctly, everything should Just Work.
> >
> > But Ben added both the generic and the x86 versions the same day, so
> > there must be some complication:
> >
> >   98d9f30c820d ("pci/of: Match PCI devices to OF nodes dynamically")
> >   3d5fe5a65af9 ("x86/devicetree: Use generic PCI <-> OF matching")
> >
> > So I guess my question is, why do we need a microblaze-specific
> > version at all?
> >
I did not notice the weak version in /pci/of.c, I have tested with weak version also and it is working.  We might not need this microblaze specific version, but will wait for ben's reply.  

Bharat