linux-kernel - Re: [PATCH 07/28] nios2: I/O Mapping

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Message-ID: <23940551.x13XR6zuRa@wuerfel>
Date:	Thu, 24 Apr 2014 09:43:52 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Ley Foon Tan <lftan@...era.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Linux-Arch <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	cltang@...esourcery.com
Subject: Re: [PATCH 07/28] nios2: I/O Mapping

On Thursday 24 April 2014 14:02:47 Ley Foon Tan wrote:
> On Tue, Apr 22, 2014 at 9:59 PM, Arnd Bergmann <arnd@...db.de> wrote:
> > On Friday 18 April 2014, Ley Foon Tan wrote:
> >
> >> +
> >> +#include <asm/pgtable-bits.h>
> >> +
> >> +#define IO_SPACE_LIMIT 0xffffffff
> >
> > Please use 0xffff here, this should work for almost any PCI bus.
> Ah, CONFIG_PCI is not enable in nios2. So, I think IO_SPACE_LIMIT
> should set to 0.

Yes, possibly with a comment added regarding PCI.

> >> +/*
> >> + *   make the short names macros so specific devices
> >> + *   can override them as required
> >> + */
> >> +#define inb(addr)            readb(addr)
> >> +#define inw(addr)            readw(addr)
> >> +#define inl(addr)            readl(addr)
> >> +#define outb(x, addr)                ((void) writeb(x, addr))
> >> +#define outw(x, addr)                ((void) writew(x, addr))
> >> +#define outl(x, addr)                ((void) writel(x, addr))
> >
> > This makes no sense: the legacy PC I/O accessors take a completely
> > different argument type: I would recommend to make both inline
> > functions so you can ensure that readl() gets passed an __iomem
> > pointer, while inl() gets an integer number.
> >
> > Please see the asm-generic version for an example. You should also
> > define a non-NULL PCI_IOBASE to which the PCI I/O space gets mapped.
> I think these macros can be removed if PCI is not enabled in Nios2.

We have a bunch of ISA device drivers that use these interfaces but
are not built conditionally through a Kconfig dependency. If you
want 'allyesconfig' to build successfully, you have to provide some
dummy implementation.

> >> +#define ioport_map(port, nr) ioremap(port, nr)
> >> +#define ioport_unmap(port)   iounmap(port)
> >
> > Use this one instead:
> >
> > #ifdef CONFIG_PCI
> > static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
> > {
> >         return PCI_IOBASE + port;
> > }
> >
> > static inline void __iomem *ioport_unmap(void __iomem *)
> > {
> > }
> > #endif
> These also can be removed.

For this, there is a Kconfig symbol. If you don't provide ioport_map,
you should set CONFIG_NO_IOPORT_MAP. Uwe Kleine-König has recently
started some work in this area. Ideally we would also have a CONFIG_HAS_IOPORT
option that is only set by architectures that actually implement inb/outb.
Getting there still needs work, but any help is appreciated.

	Arnd
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