From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: s3c2410fb: fix clockrate calculation Date: Thu, 20 Aug 2009 15:19:44 -0700 Message-ID: <20090820151944.9c29607c.akpm@linux-foundation.org> References: <20090820215047.717581584@fluff.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sfi-mx-1.v28.ch3.sourceforge.com ([172.29.28.121] helo=mx.sourceforge.net) by 335xhf1.ch3.sourceforge.com with esmtp (Exim 4.69) (envelope-from ) id 1MeFzD-0007tE-U4 for linux-fbdev-devel@lists.sourceforge.net; Thu, 20 Aug 2009 22:19:59 +0000 Received: from smtp1.linux-foundation.org ([140.211.169.13]) by 29vjzd1.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.69) id 1MeFz8-0000hH-EP for linux-fbdev-devel@lists.sourceforge.net; Thu, 20 Aug 2009 22:19:59 +0000 In-Reply-To: <20090820215047.717581584@fluff.org.uk> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-fbdev-devel-bounces@lists.sourceforge.net To: Ben Dooks Cc: linux-fbdev-devel@lists.sourceforge.net On Thu, 20 Aug 2009 22:50:47 +0100 Ben Dooks wrote: > In the final part of the calculation for the tft display clockrate we > divide the output pf s3c2410fb_calc_pixclk() by 2 which leaves us with > a rounding error if the result is odd. > > Change to using DIV_ROUND_UP() to ensure that we always choose a higher > divisor and thus a lower frequency. > > Signed-off-by: Ben Dooks > > --- > drivers/video/s3c2410fb.c | 4 +++- > 2 files changed, 5 insertions(+), 2 deletions(-) > > Index: b/drivers/video/s3c2410fb.c > =================================================================== > --- a/drivers/video/s3c2410fb.c 2009-08-20 08:45:41.000000000 +0100 > +++ b/drivers/video/s3c2410fb.c 2009-08-20 08:45:42.000000000 +0100 > @@ -369,7 +369,9 @@ static void s3c2410fb_activate_var(struc > void __iomem *regs = fbi->io; > int type = fbi->regs.lcdcon1 & S3C2410_LCDCON1_TFT; > struct fb_var_screeninfo *var = &info->var; > - int clkdiv = s3c2410fb_calc_pixclk(fbi, var->pixclock) / 2; > + int clkdiv; > + > + clkdiv = DIV_ROUND_UP(s3c2410fb_calc_pixclk(fbi, var->pixclock), 2); > > printk(KERN_INFO "%s: pixclock=%d, clkdiv=%d\n", > __func__, var->pixclock, clkdiv); The changelog forgot to tell us what the impact of this bug is, so I cannot work out whether we need this fix in 2.6.32, 2.6.31, 2.6.30.x, .... ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july