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

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Message-ID: <65ca8848-3a99-bda8-5165-9453b70316fa@deltatee.com>
Date:   Mon, 31 Jul 2017 12:00:11 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Andy Shevchenko <andy.shevchenko@...il.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 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.

Logan