linux-kernel - Re: [PATCH 2/2 v3] mmc: dw_mmc: Fix the CTO overflow calculation for 32-bit systems

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Message-ID: <CAHp75Vfb6HQvx531bDi_j1wG=-vae73o+hcOyCGfOeQKEUpYeg@mail.gmail.com>
Date:   Tue, 27 Feb 2018 12:49:06 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Jisheng Zhang <Jisheng.Zhang@...aptics.com>
Cc:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dianders@...omium.org" <dianders@...omium.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "Vineet.Gupta1@...opsys.com" <Vineet.Gupta1@...opsys.com>,
        "Eugeniy.Paltsev@...opsys.com" <Eugeniy.Paltsev@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "Evgeniy.Didin@...opsys.com" <Evgeniy.Didin@...opsys.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>
Subject: Re: [PATCH 2/2 v3] mmc: dw_mmc: Fix the CTO overflow calculation for
 32-bit systems

On Tue, Feb 27, 2018 at 5:52 AM, Jisheng Zhang
<Jisheng.Zhang@...aptics.com> wrote:
> On Mon, 26 Feb 2018 20:27:22 +0000 Alexey Brodkin wrote:
>> On Mon, 2018-02-26 at 20:30 +0200, Andy Shevchenko wrote:
>> > On Mon, Feb 26, 2018 at 7:14 PM, Evgeniy Didin
>> > <Evgeniy.Didin@...opsys.com> wrote:
>> > > On Mon, 2018-02-26 at 18:53 +0200, Andy Shevchenko wrote:
>> > > > On Mon, Feb 26, 2018 at 5:14 PM, Evgeniy Didin

>> > > > > > IIRC, someone commented on this or similar, i.e.
>> > > > > > DIV_ROUND_UP_ULL() ?

^^^^^^^^^^^^

>> So maybe we need to add export of __udivdi3() for other arches, what do you think?

> Per my understanding, Linux kernel prefer to make use of do_div or implementations
> in <linux/math64.h> for 64bit divide

To everyone in this thread. See just above. That's solution which will work.
Other than that, drop COMPILE_TEST from the Kconfig and put a comment
that driver will not compile on architectures w/o division library.

-- 
With Best Regards,
Andy Shevchenko