linux-kernel - Re: [PATCH v8 9/9] pci: Remap I/O bus resources into CPU space with pci_remap

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Message-ID: <20140715090939.GA18203@arm.com>
Date:	Tue, 15 Jul 2014 10:09:40 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Liviu Dudau <Liviu.Dudau@....com>,
	linux-pci <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Will Deacon <Will.Deacon@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v8 9/9] pci: Remap I/O bus resources into CPU space with
 pci_remap_iospace()

On Mon, Jul 14, 2014 at 07:15:48PM +0100, Arnd Bergmann wrote:
> On Monday 14 July 2014 17:54:43 Catalin Marinas wrote:
> > On Tue, Jul 01, 2014 at 07:43:34PM +0100, Liviu Dudau wrote:
> > > Introduce a default implementation for remapping PCI bus I/O resources
> > > onto the CPU address space. Architectures with special needs may
> > > provide their own version, but most should be able to use this one.
> > [...]
> > > +/**
> > > + *   pci_remap_iospace - Remap the memory mapped I/O space
> > > + *   @res: Resource describing the I/O space
> > > + *   @phys_addr: physical address where the range will be mapped.
> > > + *
> > > + *   Remap the memory mapped I/O space described by the @res
> > > + *   into the CPU physical address space. Only architectures
> > > + *   that have memory mapped IO defined (and hence PCI_IOBASE)
> > > + *   should call this function.
> > > + */
> > > +int __weak pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)
> > > +{
> > > +     int err = -ENODEV;
> > > +
> > > +#ifdef PCI_IOBASE
> > > +     if (!(res->flags & IORESOURCE_IO))
> > > +             return -EINVAL;
> > > +
> > > +     if (res->end > IO_SPACE_LIMIT)
> > > +             return -EINVAL;
> > > +
> > > +     err = ioremap_page_range(res->start + (unsigned long)PCI_IOBASE,
> > > +                             res->end + 1 + (unsigned long)PCI_IOBASE,
> > > +                             phys_addr, __pgprot(PROT_DEVICE_nGnRE));
> > 
> > Except that PROT_DEVICE_nGnRE is arm64 only. I think that's a function
> > that should remain arch specific.
> > 
> 
> How about #defining a macro with the correct pgprot value in asm/pci.h
> or asm/pgtable.h?
> We can provide a default for that in another architecture independent
> location.

That should work. We already have pgprot_noncached/writecombine in
asm-generic/pgtable.h which all architectures seem to include. The
default can be pgprot_noncached and we would invoke it as
pgprot_device(PAGE_KERNEL).

-- 
Catalin
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