From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757377AbcDLSB2 (ORCPT ); Tue, 12 Apr 2016 14:01:28 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:34429 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757242AbcDLSBZ (ORCPT ); Tue, 12 Apr 2016 14:01:25 -0400 Date: Tue, 12 Apr 2016 11:01:28 -0700 From: Guenter Roeck To: Andy Shevchenko Cc: Sudip Mukherjee , Wim Van Sebroeck , Haavard Skinnemoen , Hans-Christian Egtvedt , "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 Message-ID: <20160412180128.GA6965@roeck-us.net> References: <1460440303-20640-1-git-send-email-sudipm.mukherjee@gmail.com> <570CF2CB.2050200@roeck-us.net> <570CFA90.4060100@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: guenter@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: guenter@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 12, 2016 at 05:58:20PM +0300, Andy Shevchenko wrote: > On Tue, Apr 12, 2016 at 4:39 PM, Sudip Mukherjee > 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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html