linux-kernel - Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap

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Date:   Mon, 10 Apr 2017 15:30:42 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Arnd Bergmann <arnd@...db.de>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Richard Henderson <rth@...ddle.net>,
        Tony Luck <tony.luck@...el.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Haavard Skinnemoen <hskinnemoen@...il.com>,
        Pratyush Anand <pratyush.anand@...il.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Mingkai Hu <mingkai.hu@...escale.com>,
        John Garry <john.garry@...wei.com>,
        Tanmay Inamdar <tinamdar@....com>,
        Murali Karicheri <m-karicheri2@...com>,
        Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>,
        Ray Jui <rjui@...adcom.com>,
        Wenrui Li <wenrui.li@...k-chips.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Minghuan Lian <minghuan.Lian@...escale.com>,
        Jon Mason <jonmason@...adcom.com>,
        Gabriele Paoloni <gabriele.paoloni@...wei.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Michal Simek <michal.simek@...inx.com>,
        Stanimir Varbanov <svarbanov@...sol.com>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        Roy Zang <tie-fei.zang@...escale.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap
 interface

On Thu, Apr 06, 2017 at 11:47:37AM +0100, Russell King - ARM Linux wrote:
> On Thu, Apr 06, 2017 at 11:26:36AM +0100, Lorenzo Pieralisi wrote:
> > On Wed, Apr 05, 2017 at 01:38:12PM +0100, Lorenzo Pieralisi wrote:
> > > eg: openrisc
> > > 
> > > >> include/asm-generic/io.h:922:9: error: implicit declaration of
> > > >> function 'ioremap_nocache' [-Werror=implicit-function-declaration]
> > >      return ioremap_nocache(offset, size);
> > 
> > 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.
> 
> From what I can see:
> 
> (a) openrisc does define ioremap_nocache() in its asm/io.h
> (b) these do not:
> 
> $ grep -L 'ioremap_nocache' arch/*/include/asm/io.h
> arch/blackfin/include/asm/io.h
> arch/h8300/include/asm/io.h
> arch/m68k/include/asm/io.h
> arch/score/include/asm/io.h
> arch/sparc/include/asm/io.h
> 
> Out of those, blackfin, h8300 and score do not define it, whereas m68k
> and sparc do in other headers included by asm/io.h.  So it looks like
> we have three problem architectures that don't define an ioremap_nocache().
> 
> PCI on blackfin depends on BROKEN, so it's not selectable.  From what I
> can tell, h8300 and score do not allow PCI to be enabled (but maybe its
> buried elsewhere in their Kconfig files, I didn't check.)
> 
> So, I think a way around this is to make ioremap_nopost() conditional
> on PCI in linux/io.h for the time being - if its scope wants to be
> enlarged, then these three architectures would need to have either an
> ioremap_nopost() implementation added, or an ioremap_nocache()
> implementation.

Ok, I implemented asm-generic/ioremap-nopost.h, I do not think we need
a CONFIG_PCI guard (kbuild has not barfed at it, yet), given that
blackfin and h8300 are !MMU and score selects NO_IOMEM.

Patch below is all arches squashed into one commit, I probably have
to split it one per arch which will make this a 50-patch series in
total:

https://git.kernel.org/pub/scm/linux/kernel/git/lpieralisi/linux.git/commit/?h=pci/config-io-mappings-fix-v3&id=acc0be820c809101e02ab7cb170f802db53af934

If I hear no complaints I will split patch above one per arch and
repost the series shortly (even though I think I should make two series
out of it, one asm-generic/ioremap-nopost.h boilerplate and second
ARM/ARM64 implementation + PCI drivers).

Lorenzo