linux-kernel - Re: [PATCH] watchdog: dw

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Message-ID: <5725C698.1090504@gmail.com>
Date:	Sun, 01 May 2016 10:04:24 +0100
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Wim Van Sebroeck <wim@...ana.be>,
	Haavard Skinnemoen <hskinnemoen@...il.com>,
	Hans-Christian Egtvedt <egtvedt@...fundet.no>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kernel-testers@...r.kernel.org, linux-watchdog@...r.kernel.org,
	Chris Mason <clm@...com>
Subject: Re: [PATCH] watchdog: dw_wdt: dont build for avr32

On Sunday 01 May 2016 02:13 AM, Guenter Roeck wrote:
> On Sat, Apr 30, 2016 at 05:36:51PM -0700, Guenter Roeck wrote:
>> On Sat, Apr 30, 2016 at 07:38:28PM +0100, Sudip Mukherjee wrote:
>>> On Tue, Apr 12, 2016 at 11:01:28AM -0700, Guenter Roeck wrote:
>>>> 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@...il.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 ?
>>>
>>> Please let me know what i can do here to help solve the problem.
>>> linux-next continues to fail for avr32, and to make matters worse we
>>> also have the similar problem in btrfs.
>>>
>>> ERROR: "__avr32_udiv64" [fs/btrfs/btrfs.ko] undefined!
>>> ERROR: "__avr32_udiv64" [drivers/watchdog/kempld_wdt.ko] undefined!
>>>
>>> Adding Chris to CC if he has some idea how to solve this error for btrfs.
>>> Build log for next-20160429 is at:
>>> https://travis-ci.org/sudipm-mukherjee/parport/jobs/126581065
>>>
>>
>> Try the patch below.
>>
>> Guenter
>>
> Sorry, patch wasn't complete.
>
> Guenter
>
> ---
>  From c684f2cf54ecb256007288af23c24bfcdb2bbace Mon Sep 17 00:00:00 2001
> From: Guenter Roeck <linux@...ck-us.net>
> Date: Sat, 30 Apr 2016 17:29:14 -0700
> Subject: [PATCH] avr32: __div64_const32 is not ok
>
> Building avr32 images may fail with errors such as
>
> ERROR: "__avr32_udiv64" [fs/btrfs/btrfs.ko] undefined!
> ERROR: "__avr32_udiv64" [drivers/watchdog/kempld_wdt.ko] undefined!
>
> gcc for avr32 generates those symbols for certain constants used
> as divisor in do_div(). The problem can be avoided by setting
> __div64_const32_is_OK to false for the architecture.
>
> Cc: Sudip Mukherjee <sudipm.mukherjee@...il.com>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
>   arch/avr32/include/asm/Kbuild  | 1 -
>   arch/avr32/include/asm/div64.h | 3 +++
>   2 files changed, 3 insertions(+), 1 deletion(-)
>   create mode 100644 arch/avr32/include/asm/div64.h
>
> diff --git a/arch/avr32/include/asm/Kbuild b/arch/avr32/include/asm/Kbuild
> index 241b9b9729d8..d2be4688ac7b 100644
> --- a/arch/avr32/include/asm/Kbuild
> +++ b/arch/avr32/include/asm/Kbuild
> @@ -3,7 +3,6 @@ generic-y += clkdev.h
>   generic-y += cputime.h
>   generic-y += delay.h
>   generic-y += device.h
> -generic-y += div64.h
>   generic-y += emergency-restart.h
>   generic-y += exec.h
>   generic-y += futex.h
> diff --git a/arch/avr32/include/asm/div64.h b/arch/avr32/include/asm/div64.h
> new file mode 100644
> index 000000000000..1f3328e178df
> --- /dev/null
> +++ b/arch/avr32/include/asm/div64.h
> @@ -0,0 +1,3 @@
> +#define __div64_const32_is_OK	false
> +
> +#include <asm-generic/div64.h>
>

It looks like this patch has fixed about the error about the watchdog 
but for some reason I am still getting the error about the btrfs.

ERROR: "__avr32_udiv64" [fs/btrfs/btrfs.ko] undefined!

regards
sudip