linux-kernel - Re: [PATCH -next] fbdev: radeon: Avoid 64 bit divide

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Message-ID: <1433798517.4526.170.camel@kernel.crashing.org>
Date:	Tue, 09 Jun 2015 07:21:57 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tina Ruchandani <ruchandani.tina@...il.com>
Subject: Re: [PATCH -next] fbdev: radeon: Avoid 64 bit divide

On Fri, 2015-06-05 at 13:23 -0700, Guenter Roeck wrote:
> On 06/05/2015 01:08 PM, Benjamin Herrenschmidt wrote:
> > On Fri, 2015-06-05 at 11:05 -0700, Guenter Roeck wrote:
> >> A 64 bit divide causes build failures with 32 bit builds, such as
> >>
> >> ERROR: "__divdi3" [drivers/video/fbdev/aty/radeonfb.ko] undefined!
> >>
> >> or
> >>
> >> drivers/built-in.o: In function `radeon_probe_pll_params':
> >> radeon_base.c:(.text+0x16608b): undefined reference to `__divdi3'
> >
> > What about using do_div() instead ?
> >
> 
> delta is known to be <= 10*1000000, so I figured that would have been overkill.
> But, sure, at the end it is the same. Want me to resubmit ?

Don't bother.

> Guenter
> 
> >> Fixes: ce8f4069dce8 ("fbdev: radeon: Remove 'struct timeval' usage")
> >> Cc: Tina Ruchandani <ruchandani.tina@...il.com>
> >> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> >> ---
> >>   drivers/video/fbdev/aty/radeon_base.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/video/fbdev/aty/radeon_base.c b/drivers/video/fbdev/aty/radeon_base.c
> >> index b3612e30d74f..374e47532035 100644
> >> --- a/drivers/video/fbdev/aty/radeon_base.c
> >> +++ b/drivers/video/fbdev/aty/radeon_base.c
> >> @@ -492,7 +492,7 @@ static int radeon_probe_pll_params(struct radeonfb_info *rinfo)
> >>   	/* Return -1 if more than 10 seconds have elapsed */
> >>   	if (delta > (10*1000000))
> >>   		return -1;
> >> -	hz = 1000000/delta;
> >> +	hz = 1000000 / (int)delta;
> >>
> >>   	hTotal = ((INREG(CRTC_H_TOTAL_DISP) & 0x1ff) + 1) * 8;
> >>   	vTotal = ((INREG(CRTC_V_TOTAL_DISP) & 0x3ff) + 1);
> >
> >
> >


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