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

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Date:   Thu, 6 Apr 2017 18:19:19 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        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>
Subject: Re: [PATCH v2 02/22] asm-generic/io.h: add ioremap_nopost remap
 interface

On Thu, Apr 06, 2017 at 06:09:51PM +0100, Lorenzo Pieralisi wrote:
> On Thu, Apr 06, 2017 at 05:40:16PM +0100, Russell King - ARM Linux wrote:
> > On Thu, Apr 06, 2017 at 05:21:56PM +0100, Lorenzo Pieralisi wrote:
> > > Ok, so:
> > > 
> > > (1) I can do asm-generic/ioremap-nopost.h, which I assume you want to
> > >     contain something like
> > > 
> > > static inline void __iomem *ioremap_nopost(phys_addr_t offset, size_t size)
> > > {
> > > 	return ioremap_nocache(offset, size);
> > > }
> > > 
> > > Funny bit is that it has to be included by asm*/io.h files _after_
> > > ioremap_nocache has been #defined (that's the reason my approach was
> > > failing miserably even on arches like eg powerpc (see [1] below) that
> > > does have ioremap_nocache),
> > 
> > PowerPC does have ioremap_nocache() though:
> > 
> > /**
> >  * ioremap     -   map bus memory into CPU space
> > ...
> >  * * ioremap_nocache is identical to ioremap
> > extern void __iomem *ioremap(phys_addr_t address, unsigned long size);
> > #define ioremap_nocache(addr, size)     ioremap((addr), (size))
> > 
> > and this include file is included very early on in linux/io.h.  I don't
> > see anything that conditionalises it on anything except __KERNEL__.  So,
> > the report from 0-day really doesn't make any sense to me.
> > 
> > Do we know how we're ending up in linux/io.h line 169 without having
> > picked up the ioremap_nocache() definition provided by PowerPC's
> > asm/io.h ?
> 
> I will debug it further but I *think* it is because:
> 
> eg arch/powerpc/oprofile/op_model_cell.c includes <asm/io.h>
> 
> and <asm/io.h> includes <linux/io.h> before ioremap_nocache is defined

Oh, that's just very wrong.  asm/foo.h should never include linux/foo.h
especially when linux/foo.h already includes asm/foo.h.  I think we
need PowerPC folk to fix this.

-- 
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