netdev - Re: RFC on writel and writel

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Message-ID: <CAK8P3a2qcXmPx-j6XZPGhWZ_K3=cBym8tVFzwcZMSCjVfzMs1g@mail.gmail.com>
Date:   Thu, 29 Mar 2018 18:29:32 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     David Miller <davem@...emloft.net>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Will Deacon <will.deacon@....com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        David Laight <David.Laight@...lab.com>,
        "Oliver O'Halloran" <oohall@...il.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Alexander Duyck <alexander.h.duyck@...hat.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Networking <netdev@...r.kernel.org>,
        Linus Torvalds <linus971@...il.com>
Subject: Re: RFC on writel and writel_relaxed

On Thu, Mar 29, 2018 at 3:56 PM, Sinan Kaya <okaya@...eaurora.org> wrote:
> On 3/28/2018 11:55 AM, David Miller wrote:
>> From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> Date: Thu, 29 Mar 2018 02:13:16 +1100
>>
>>> Let's fix all archs, it's way easier than fixing all drivers. Half of
>>> the archs are unused or dead anyway.
>>
>> Agreed.
>>
>
> I pinged most of the maintainers yesterday.
> Which arches do we care about these days?
> I have not been paying attention any other architecture besides arm64.
>
> arch            status                  detail
> ------          -------------           ------------------------------------
> alpha           question sent

I'm guessing alpha has problems

extern inline u32 readl(const volatile void __iomem *addr)
{
        u32 ret = __raw_readl(addr);
        mb();
        return ret;
}
extern inline void writel(u32 b, volatile void __iomem *addr)
{
        __raw_writel(b, addr);
        mb();
}

There is a barrier in writel /after/ the acess but not before.

> arc             question sent           ysato@...rs.sourceforge.jp will fix it.
> arm             no issues
> arm64           no issues
> blackfin        question sent           about to be removed
> c6x             question sent

no PCI, so it might not matter that much -- all drivers
are platform specific in the end.

> cris            question sent
> frv

cris and frv are getting removed

> h8300           question sent

no PCI

> hexagon         question sent

no PCI

> ia64            no issues               confirmed by Tony Luck
> m32r

removed

> m68k            question sent

> metag

removed

> microblaze      question sent
> mips            question sent

I'm guessing that some mips platforms have problems, but others don't.

> mn10300         question sent

removed

> nios2           question sent

no PCI

> openrisc        no issues               shorne@...il.com says should no issues
> parisc          no issues               grantgrundler@...il.com says most probably no problem but still looking
> powerpc         no issues
> riscv           question sent

riscv should be fine

> s390            question sent

Pretty sure this is also fine

> score           question sent

removed

> sh              question sent
> sparc           question sent

> tile            question sent

removed

> unicore32       question sent

Note the maintainer's new email address in linux-next.

> x86             no issues

> xtensa          question sent

removed.

         Arnd