From: Guenter Roeck <linux@roeck-us.net>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>,
Wim Van Sebroeck <wim@iguana.be>,
Haavard Skinnemoen <hskinnemoen@gmail.com>,
Hans-Christian Egtvedt <egtvedt@samfundet.no>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
kernel-testers@vger.kernel.org, linux-watchdog@vger.kernel.org
Subject: Re: [PATCH] watchdog: dw_wdt: dont build for avr32
Date: Tue, 12 Apr 2016 11:01:28 -0700 [thread overview]
Message-ID: <20160412180128.GA6965@roeck-us.net> (raw)
In-Reply-To: <CAHp75VcrmiP0GWR-zCBmqc7zA6uiC4dD8-HDikmWZxyEwXkRLw@mail.gmail.com>
On Tue, Apr 12, 2016 at 05:58:20PM +0300, Andy Shevchenko wrote:
> On Tue, Apr 12, 2016 at 4:39 PM, Sudip Mukherjee
> <sudipm.mukherjee@gmail.com> wrote:
> > On Tuesday 12 April 2016 06:36 PM, Guenter Roeck wrote:
> >>
> >> On 04/11/2016 10:51 PM, Sudip Mukherjee wrote:
> >>>
> >>> The build of avr32 allmodconfig fails with the error:
> >>> ERROR: "__avr32_udiv64" [drivers/watchdog/kempld_wdt.ko] undefined!
> >>>
> >> This means there is a direct 64 bit divide operation in the driver,
> >> which we should identify and fix.
>
> This driver will quite likely never be used on AVR32. Do we need to
> fix this due to some other architectures?
>
> > yes, there is.
> >
> > in function: kempld_wdt_set_stage_timeout()
> > remainder = do_div(stage_timeout64, prescaler);
>
> > Any idea how to fix it?
>
> Not easy, however, prescaler value is ((1 << 21) - 1) which someone
> might consider as (1 << 21) with lost in precision.
>
> Thus, shift on 20 bits right, add last bit to the value and shift on 1
> bit right more.
>
Sorry, I am missing something. do_div() should work fine with any 32 bit value
as divisor, no matter what that value is. Why does it fail here ? And why does
it work if I pass 0x1fffff as second parameter to do_div() directly ?
Thanks,
Guenter
> --
> With Best Regards,
> Andy Shevchenko
> --
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next prev parent reply other threads:[~2016-04-12 18:01 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-12 5:51 [PATCH] watchdog: dw_wdt: dont build for avr32 Sudip Mukherjee
2016-04-12 13:06 ` Guenter Roeck
2016-04-12 13:39 ` Sudip Mukherjee
2016-04-12 14:58 ` Andy Shevchenko
2016-04-12 15:29 ` Sudip Mukherjee
2016-04-12 18:01 ` Guenter Roeck [this message]
2016-04-12 18:17 ` Andy Shevchenko
2016-04-30 18:38 ` Sudip Mukherjee
2016-05-01 0:04 ` Guenter Roeck
2016-05-01 0:36 ` Guenter Roeck
2016-05-01 1:13 ` Guenter Roeck
2016-05-01 9:04 ` Sudip Mukherjee
2016-05-01 14:09 ` Guenter Roeck
2016-05-01 16:30 ` Sudip Mukherjee
2016-04-12 13:07 ` Guenter Roeck
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