Message-ID: <20140227164857.GQ1692@e106497-lin.cambridge.arm.com>
Date:	Thu, 27 Feb 2014 16:48:57 +0000
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	linux-pci <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 3/3] arm64: Add architecture support for PCI

On Thu, Feb 27, 2014 at 04:06:24PM +0000, Arnd Bergmann wrote:
> On Thursday 27 February 2014 13:09:59 Liviu Dudau wrote:
> 
> > +/*
> > + * PCI address space differs from physical memory address space
> > + */
> > +#define PCI_DMA_BUS_IS_PHYS	(0)
> > +
> > +extern int isa_dma_bridge_buggy;
> 
> I got curious about isa_dma_bridge_buggy: apparently this is a quirk for
> some old x86 bridges. We don't have those on arm64, and we also don't have
> ISA_DMA_API, so just define this to (0).

OK.

> 
> > +static inline int pci_domain_nr(struct pci_bus *bus)
> > +{
> > +	struct pci_host_bridge *bridge = to_pci_host_bridge(bus->bridge);
> > +
> > +	if (bridge)
> > +		return bridge->domain_nr;
> > +
> > +	return 0;
> > +}
> > +
> > +static inline int pci_proc_domain(struct pci_bus *bus)
> > +{
> > +	return pci_domain_nr(bus);
> > +}
> 
> And this one I would change to always return '1': we can deal with
> domain numbers showing up in /procfs for all buses, since there is
> no legacy software to worry about.

Will do, thanks for reviewing this.

> 
> > diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> > new file mode 100644
> > index 0000000..496df41
> > --- /dev/null
> > +++ b/arch/arm64/kernel/pci.c
> > @@ -0,1 +1,126 @@
> 
> Ok, this is nice and short. Let's see if we can reduce it to nothing ;-)
> 
> > +/*
> > + * Called after each bus is probed, but before its children are examined
> > + */
> > +void pcibios_fixup_bus(struct pci_bus *bus)
> > +{
> > +	struct pci_dev *dev;
> > +	struct resource *res;
> > +	int i;
> > +
> > +	if (!pci_is_root_bus(bus)) {
> > +		pci_read_bridge_bases(bus);
> > +
> > +		pci_bus_for_each_resource(bus, res, i) {
> > +			if (!res || !res->flags || res->parent)
> > +				continue;
> > +
> > +			/*
> > +			 * If we are going to reassign everything, we can
> > +			 * shrink the P2P resource to have zero size to
> > +			 * save space
> > +			 */
> > +			if (pci_has_flag(PCI_REASSIGN_ALL_RSRC)) {
> > +				res->flags |= IORESOURCE_UNSET;
> > +				res->start = 0;
> > +				res->end = -1;
> > +				continue;
> > +			}
> > +		}
> > +	}
> > +
> > +	list_for_each_entry(dev, &bus->devices, bus_list) {
> > +		/* Ignore fully discovered devices */
> > +		if (dev->is_added)
> > +			continue;
> > +
> > +		set_dev_node(&dev->dev, pcibus_to_node(dev->bus));
> > +
> > +		/* Read default IRQs and fixup if necessary */
> > +		dev->irq = of_irq_parse_and_map_pci(dev, 0, 0);
> > +	}
> > +}
> > +EXPORT_SYMBOL(pcibios_fixup_bus);
> 
> Shrinking the P2P resources I suppose is optional, but everything
> else is in fact needed for any DT based architecture. Could this
> be turned into a generic helper function in the PCI core that we
> can call from architecture code?
> 
> If you name it pci_generic_fixup_bus(), we can add a weak helper
> like:
> 
> void __weak pcibios_fixup_bus(struct pci_bus *bus)
> {
> 	pci_generic_fixup_bus(bus);
> }
> 
> for architectures like arm64 that don't actually need to do anything
> else.

Sure, it can be done. Don't know what is the policy for these kind of functions
that are used by architectures, but I can try sending a patch that adds the
weak implementations in the core PCI code.

> 
> > +/*
> > + * We don't have to worry about legacy ISA devices, so nothing to do here
> > + */
> > +resource_size_t pcibios_align_resource(void *data, const struct resource *res,
> > +				resource_size_t size, resource_size_t align)
> > +{
> > +	return ALIGN(res->start, align);
> > +}
> > +EXPORT_SYMBOL(pcibios_align_resource);
> 
> Where did this come from? 

>From an internal version that Will posted. See, we do talk to each other ;)


> The most common implementation seems to be
> 
> resource_size_t pcibios_align_resource(void *data, const struct resource *res,
> 				resource_size_t size, resource_size_t align)
> {
> 	return start;
> }
> EXPORT_SYMBOL(pcibios_align_resource);
> 
> if you don't have to worry about ISA devices. The ALIGN() part seems to
> be handled by __find_resource() already.
> 
> I'd say that should be made the default implementation in the PCI core.
> 
> I'm also pretty sure you don't need the EXPORT_SYMBOL, since the PCI
> core cannot be a loadable module (yet).

OK.

> 
> > +int pcibios_enable_device(struct pci_dev *dev, int mask)
> > +{
> > +	return pci_enable_resources(dev, mask);
> > +}
> > +
> > +void pcibios_fixup_bridge_ranges(struct list_head *resources)
> > +{
> > +}
> 
> These are clearly the right implementations, but they should be weak
> functions, too.

pcibios_enable_devices is already subject to a patch series from Bjorn that make
the weak implementation do the right thing for arm64, so the final version will
not contain this.

> 
> > +#define IO_SPACE_PAGES	((IO_SPACE_LIMIT + 1) / PAGE_SIZE)
> > +static DECLARE_BITMAP(pci_iospace, IO_SPACE_PAGES);
> > +
> > +unsigned long pci_ioremap_io(const struct resource *res, phys_addr_t phys_addr)
> > +{
> > +	unsigned long start, len, virt_start;
> > +	int err;
> > +
> > +	if (res->end > IO_SPACE_LIMIT)
> > +		return -EINVAL;
> > +
> > +	/*
> > +	 * try finding free space for the whole size first,
> > +	 * fall back to 64K if not available
> > +	 */
> > +	len = resource_size(res);
> > +	start = bitmap_find_next_zero_area(pci_iospace, IO_SPACE_PAGES,
> > +				res->start / PAGE_SIZE, len / PAGE_SIZE, 0);
> > +	if (start == IO_SPACE_PAGES && len > SZ_64K) {
> > +		len = SZ_64K;
> > +		start = 0;
> > +		start = bitmap_find_next_zero_area(pci_iospace, IO_SPACE_PAGES,
> > +					start, len / PAGE_SIZE, 0);
> > +	}
> > +
> > +	/* no 64K area found */
> > +	if (start == IO_SPACE_PAGES)
> > +		return -ENOMEM;
> > +
> > +	/* ioremap physical aperture to virtual aperture */
> > +	virt_start = start * PAGE_SIZE + (unsigned long)PCI_IOBASE;
> > +	err = ioremap_page_range(virt_start, virt_start + len,
> > +				phys_addr, __pgprot(PROT_DEVICE_nGnRE));
> > +	if (err)
> > +		return err;
> > +
> > +	bitmap_set(pci_iospace, start, len / PAGE_SIZE);
> > +
> > +	/* return io_offset */
> > +	return start * PAGE_SIZE - res->start;
> > +}
> 
> Maybe this can become an optional helper function with a separate Kconfig symbol
> to enable it.

Probably need to find a different name for it as well when it moves into core, arm
already has an externalised function with this name.

Best regards,
Liviu

> 
> 	Arnd
> 
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

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