From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Dooks Subject: Re: s3c2410fb: fix clockrate calculation Date: Thu, 27 Aug 2009 10:57:24 +0100 Message-ID: <4A965884.4030802@simtec.co.uk> References: <20090820215047.717581584@fluff.org.uk> <20090820151944.9c29607c.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sfi-mx-4.v28.ch3.sourceforge.com ([172.29.28.124] helo=mx.sourceforge.net) by 335xhf1.ch3.sourceforge.com with esmtp (Exim 4.69) (envelope-from ) id 1Mgbjy-0005a8-OV for linux-fbdev-devel@lists.sourceforge.net; Thu, 27 Aug 2009 09:57:58 +0000 Received: from aeryn.fluff.org.uk ([87.194.8.8] helo=kira.home.fluff.org) by 1b2kzd1.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.69) id 1Mgbju-0005ZJ-4g for linux-fbdev-devel@lists.sourceforge.net; Thu, 27 Aug 2009 09:57:58 +0000 In-Reply-To: <20090820151944.9c29607c.akpm@linux-foundation.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-fbdev-devel-bounces@lists.sourceforge.net To: Andrew Morton Cc: linux-fbdev-devel@lists.sourceforge.net Andrew Morton wrote: > 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, .... Sorry, found this whilst working on a new machine and the pix clock being too fast for the display. The machine is not yet merged into the mainline so this not an important fix. -- Ben Dooks, Software Engineer, Simtec Electronics http://www.simtec.co.uk/ ------------------------------------------------------------------------------ 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