linux-kernel - Re: [PATCH] arm64: Add architecture support for PCI

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Date:	Tue, 4 Feb 2014 17:18:41 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Andrew Murray <amurray@...edded-bits.co.uk>
Cc:	"linux-pci" <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	"linaro-kernel" <linaro-kernel@...ts.linaro.org>
Subject: Re: [PATCH] arm64: Add architecture support for PCI

On Tuesday 04 February 2014, Andrew Murray wrote:
> On 4 February 2014 12:29, Liviu Dudau <Liviu.Dudau@....com> wrote:
> > On Mon, Feb 03, 2014 at 10:34:40PM +0000, Andrew Murray wrote:
> >> On 3 February 2014 18:43, Liviu Dudau <Liviu.Dudau@....com> wrote:
> >> > diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
> >> > index 4cc813e..ce5bad2 100644
> >> > --- a/arch/arm64/include/asm/io.h
> >> > +++ b/arch/arm64/include/asm/io.h
> >> > @@ -120,9 +120,13 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
> >> >  /*
> >> >   *  I/O port access primitives.
> >> >   */
> >> > +#define arch_has_dev_port()    (0)
> >> >  #define IO_SPACE_LIMIT         0xffff
> >> >  #define PCI_IOBASE             ((void __iomem *)(MODULES_VADDR - SZ_2M))
> >> >
> >> > +#define ioport_map(port, nr)   (PCI_IOBASE + ((port) & IO_SPACE_LIMIT))
> >> > +#define ioport_unmap(addr)
> >>
> >> I'm not sure that this will work. The in[bwl], out[bwl] macros in
> >> arch/arm64/include/asm/io.h already add the PCI_IOBASE offset.
> >>
> >> Instead of these two #defines, why not just enforce that
> >> GENERIC_PCI_IOMAP is enabled? Or at least wrap these defines with 'if
> >> (!config_enabled(CONFIG_GENERIC_PCI_IOMAP))' or similar.
> >
> > GENERIC_PCI_IOMAP is enabled for AArch64. We have select GENERIC_IOMAP in
> > arch/arm64/Kconfig which in turn selects GENERIC_PCI_IOMAP in lib/Kconfig.
> 
> Sorry, it was intent to suggest using the ioport_[map|unmap] functions
> in lib/iomap.c instead of defining something similar here. I guess you
> will also need to also define CONFIG_HAS_IOPORT for this to happen.

We do want CONFIG_HAS_IOPORT, but I would say that we should not use
CONFIG_GENERIC_IOMAP. As I explained in another reply, enabling this
was probably a simple mistake, and we only need this if we want I/O
spaces that are /not/ memory mapped. IMHO any ARM64 system that doesn't
map its PCI I/O space into MMIO space can live without I/O port
access.

	Arnd
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