# Re: \[Y2038\] \[PATCH\] fbdev: radeon: Remove 'struct timeval' usage

- From: Arnd Bergmann \<arnd@arndb.de\>
- Date: 2015-06-05 21:12:29 
- List: linux-fbdev
- Page: https://ratatoskr.run/linux-fbdev/2015/06/4510329
- Thread: https://ratatoskr.run/linux-fbdev/2015/06/4509675/t.md

```text
On Friday 05 June 2015 00:55:05 Tina Ruchandani wrote:
> >>> +     hz = 1000000/delta;
> >
> > This needs to be on of the do_div family.
> >
> > Dave.
> 
> Hi Dave,
> I build-tested the patch for both 32-bit and 64-bit x86. If my
> understanding is correct, since the divisor is 64-bit here, the
> compiler will do "if (delta > 1000000) hz = 0; else hz > 1000000/(s32)delta" automatically?
> In general, is this a good thumb-rule to follow - use do_div if the
> dividend is 64-bit, and normal divide operator if only the divisor is
> 64-bit?
> 

I got a build error on 32-bit arm now. There is already a check
for an overflow of 10 seconds in there (10 million microseconds),
so it is safe to do the easiest fix is to cast that microsecond
value to a u32.

	Arnd
```