Re: [2.6.25 patch] drivers/crypto/hifn_795x.c: fix 64bit division

Andrew Morton
2008-02-27T07:05:08Z

On Wed, 27 Feb 2008 08:22:07 +0200 Adrian Bunk <bunk@kernel.org> wrote:

> On Tue, Feb 26, 2008 at 04:04:39PM -0800, Andrew Morton wrote:
> > On Tue, 26 Feb 2008 21:52:40 +0300 Evgeniy Polyakov <johnpol@2ka.mipt.ru> wrote:
> >
> > > Hi Adrian.
> > >
> > > On Tue, Feb 26, 2008 at 05:34:21PM +0200, Adrian Bunk (bunk@kernel.org) wrote:
> > > > Using ndelay() with a 64bit variable as parameter can result in build
> > > > errors like the following on some 32bit systems when it results in a
> > > > 64bit division:
> > > >
> > > > <-- snip -->
> > > >
> > > > ...
> > > > MODPOST 759 modules
> > > > ERROR: "__divdi3" [drivers/crypto/hifn_795x.ko] undefined!
> > > >
> > > > <-- snip -->
> > > >
> > > > Reported by Martin Michlmayr.
> > > >
> > > > Signed-off-by: Adrian Bunk <bunk@kernel.org>
> > >
> > > Yep, ndelay() uses division, thanks a lot Adrian for spotting this.
> >
> > hm. Where?
> >...
>
> include/linux/delay.h:35
>

well found.

Something like this:

--- a/include/linux/delay.h~a
+++ a/include/linux/delay.h
@@ -7,10 +7,12 @@
* Delay routines, using a pre-computed "loops_per_jiffy" value.
*/

-extern unsigned long loops_per_jiffy;
+#include <linux/kernel.h>

#include <asm/delay.h>

+extern unsigned long loops_per_jiffy;
+
/*
* Using udelay() for intervals greater than a few milliseconds can
* risk overflow for high loops_per_jiffy (high bogomips) machines. The
@@ -32,7 +34,11 @@ extern unsigned long loops_per_jiffy;
#endif

#ifndef ndelay
-#define ndelay(x) udelay(((x)+999)/1000)
+static inline void ndelay(unsigned long x)
+{
+ udelay(DIV_ROUND_UP(x, 1000));
+}
+#define ndelay(x) ndelay(x)
#endif

void calibrate_delay(void);
_