linux-kernel - Re: [PATCH v5 3/6] iomap: introduce io{read|write}64_{lo_hi|hi

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Message-ID: <CAHp75VdOh+aa771g=T-f=XMkS5nY-7VFK6miqyxw0dOA8YOJyw@mail.gmail.com>
Date:   Mon, 31 Jul 2017 21:03:03 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        linux-ntb@...glegroups.com,
        linux-crypto <linux-crypto@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Horia Geantă <horia.geanta@....com>,
        Stephen Bates <sbates@...thlin.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Suresh Warrier <warrier@...ux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>
Subject: Re: [PATCH v5 3/6] iomap: introduce io{read|write}64_{lo_hi|hi_lo}

On Mon, Jul 31, 2017 at 9:00 PM, Logan Gunthorpe <logang@...tatee.com> wrote:
> On 31/07/17 11:58 AM, Andy Shevchenko wrote:
>> On Mon, Jul 31, 2017 at 7:31 PM, Logan Gunthorpe <logang@...tatee.com> wrote:
>>> On 31/07/17 10:10 AM, Andy Shevchenko wrote:
>>>> Some drivers (hardware) would like to have non-atomic MMIO accesses
>>>> when readq() defined
>>>
>>> Huh? But that's the whole point of the io64-nonatomic header. If a
>>> driver wants a specific non-atomic access they should just code two 32
>>> bit accesses.
>
>> You mean to call them directly as lo_hi_XXX() or hi_lo_XXX() ?
>> Yes it would work.
>
> I suppose you could do that too but I really meant just using two io32
> calls. That's the most explicit way to indicate you want a non-atomic
> access.

Per commit 3a044178cccf they are exactly created for this kind of cases.

-- 
With Best Regards,
Andy Shevchenko