linux-kernel - Re: [PATCH v6 1/3] Fix ioport_map() for !CONFIG_GENERIC

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Date:	Fri, 7 Mar 2014 01:44:52 +0000
From:	Liviu Dudau <liviu@...au.co.uk>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Arnd Bergmann <arnd@...db.de>, Liviu Dudau <Liviu.Dudau@....com>,
	linux-pci <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Tanmay Inamdar <tinamdar@....com>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 1/3] Fix ioport_map() for !CONFIG_GENERIC_IOMAP cases.

On Fri, Mar 07, 2014 at 01:09:50AM +0000, Russell King - ARM Linux wrote:
> On Fri, Mar 07, 2014 at 01:37:38AM +0100, Arnd Bergmann wrote:
> > On Thursday 06 March 2014, Russell King - ARM Linux wrote:
> > > On Wed, Mar 05, 2014 at 11:49:08AM +0000, Liviu Dudau wrote:
> > > > The inline version of ioport_map() that gets used when !CONFIG_GENERIC_IOMAP
> > > > is wrong. It returns a mapped (i.e. virtual) address that can start from
> > > > zero and completely ignores the PCI_IOBASE and IO_SPACE_LIMIT that most
> > > > architectures that use !CONFIG_GENERIC_MAP define.
> > > 
> > > What value does PCI_IOBASE and IO_SPACE_LIMIT have on other architectures
> > > who make use of asm-generic/io.h ?
> > > 
> > > $ git grep asm-generic/io.h arch/
> > > arch/arc/include/asm/io.h:#include <asm-generic/io.h>
> > 
> > PCI support hasn't been upstreamed.
> > 
> > > arch/blackfin/include/asm/io.h:#include <asm-generic/io.h>
> > > arch/metag/include/asm/io.h:#include <asm-generic/io.h>
> > 
> > No PCI support
> > 
> > > arch/microblaze/include/asm/io.h:/* from asm-generic/io.h */
> > 
> > PCI_IOBASE=0, IO_SPACE_LIMIT=0xffffffff, so no change.
> 
> Seems to define _IO_BASE not PCI_IOBASE.
> 
> > > arch/openrisc/include/asm/io.h:#include <asm-generic/io.h>
> > 
> > No PCI support
> > 
> > > arch/s390/include/asm/io.h:#include <asm-generic/io.h>
> > 
> > s390 supports PCI but no I/O space
> > 
> > > arch/score/include/asm/io.h:#include <asm-generic/io.h>
> > 
> > No PCI support
> > 
> > > arch/unicore32/include/asm/io.h:#include <asm-generic/io.h>
> > 
> > unicore32 is broken currently, the patch fixes it.
> > 
> > > arch/xtensa/include/asm/io.h:#include <asm-generic/io.h>
> > 
> > PCI_IOBASE=0, IO_SPACE_LIMIT=0xffffffff, so no change.
> 
> Doesn't appear to define PCI_IOBASE.
> 
> Maybe there's other patches required for these?
> 
> > For most of these, I assume we actually want to remove support
> > for inb/outb as they don't support I/O space accesses. The other
> > ones look correct to me.
> 
> Right, so:
> 
> #ifdef CONFIG_HAS_IOPORT
> #ifndef CONFIG_GENERIC_IOMAP
> static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
> {
>         return (void __iomem *) port;
> }
> 
> changing that to include PCI_IOBASE in there will result in a build
> failure if the C compiler sees that.  In other words, when HAS_IOPORT=y
> and GENERIC_IOMAP=n.
> 
> HAS_IOPORT is set when HAS_IOMEM is also set and NO_IOPORT unset.
> 
> It looks to me like blackfin doesn't set NO_IOPORT nor NO_IOMEM, so
> this would have HAS_IOPORT set, and from what I can see doesn't set
> GENERIC_IOMAP.  So, this change probably breaks blackfin.
> 
> I haven't looked deeply at the others.

Maybe I'm missing something obvious, but line 118 in include/asm-generic/io.h has:

#ifndef PCI_IOBASE
#define PCI_IOBASE ((void __iomem *)0)
#endif

That doesn't seem to be guarded by any other #ifdef (other than the overall
__ASM_GENERIC_IO_H), so PCI_IOBASE is defined regardless of CONFIG_HAS_IOPORT and 
CONFIG_GENERIC_IOMAP values.

Best regards,
Liviu

> 
> -- 
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