Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap interface

From	Russell King - ARM Linux <linux@armlinux.org.uk>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap interface
Date	2017-04-06 14:20 +0200
Message-ID	<tteyl-8ob-17@gated-at.bofh.it> (permalink)
References	(3 earlier) <tq0BA-A0-33@gated-at.bofh.it> <tsQZ4-1SD-15@gated-at.bofh.it> <tsSxP-2F7-5@gated-at.bofh.it> <ttcPU-7fO-21@gated-at.bofh.it> <ttdiV-7pf-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Apr 06, 2017 at 12:53:12PM +0200, Luis R. Rodriguez wrote:
> On Thu, Apr 06, 2017 at 11:26:36AM +0100, Lorenzo Pieralisi wrote:
> > Indeed, the static inline ioremap_nocache() fallback does not work
> > on all arches (whether I add the fallback in linux/io.h or
> > asm-generic/io.h is irrelevant), I bump into issues such as the one
> > reported above.
> 
> Its also not *safe* to assume on behalf of all architectures a new ioremap
> call is both a good idea and proper.

You may be right in general, but not in this case.

Currently, many drivers use plain ioremap() to map this resource.  We
are replacing that existing call - which is known to work in the majority
of cases - with a new call to cater for different semantics required by
an architecture.

Doing a replace of these ioremap() calls with ioremap_nopost() in this
situation, and then having ioremap_nopost() fail is a recipe for causing
lots and lots of regressions.

The only sane approach is to have ioremap_post() default to modelling the
_existing_ behaviour everywhere that it is used.

Requiring it to fail until architecture folk trip over the failure is
totally insane, and I very strongly disagree with you on this.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

Thread

Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Bjorn Helgaas <helgaas@kernel.org> - 2017-03-28 03:50 +0200
  Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-03-28 16:50 +0200
    Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Bjorn Helgaas <helgaas@kernel.org> - 2017-03-30 18:50 +0200
    Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-04-05 13:10 +0200
      Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-05 14:50 +0200
        Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-06 12:30 +0200
          Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-04-06 12:50 +0200
            Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-10 16:40 +0200
          Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-04-06 13:00 +0200
            Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-06 13:40 +0200
              Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-04-06 14:00 +0200
                Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-04-06 15:10 +0200
                Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-06 18:30 +0200
                Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-04-06 18:50 +0200
                Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-06 19:20 +0200
                Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-04-06 19:30 +0200
            Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-04-06 14:20 +0200
              Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap  interface "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-04-06 14:30 +0200

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