From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH] atyfb: Replace busy loop with mdelay() Date: Mon, 5 Mar 2007 15:53:18 -0800 Message-ID: <20070305155318.23fff053.akpm@linux-foundation.org> References: <20070222002033.GA26166@sci.fi> Reply-To: linux-fbdev-devel@lists.sourceforge.net Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1HON18-0000Kk-Bx for linux-fbdev-devel@lists.sourceforge.net; Mon, 05 Mar 2007 15:54:58 -0800 Received: from smtp.osdl.org ([65.172.181.24]) by mail.sourceforge.net with esmtps (TLSv1:DES-CBC3-SHA:168) (Exim 4.44) id 1HON15-0003jF-PU for linux-fbdev-devel@lists.sourceforge.net; Mon, 05 Mar 2007 15:54:58 -0800 In-Reply-To: <20070222002033.GA26166@sci.fi> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-fbdev-devel-bounces@lists.sourceforge.net Errors-To: linux-fbdev-devel-bounces@lists.sourceforge.net To: Ville =?ISO-8859-1?Q?Syrj=E4l=E4?= Cc: jsimmons@infradead.org, linux-fbdev-devel@lists.sourceforge.net, stable@kernel.org, adaplas@gmail.com, alex.kern@gmx.de On Thu, 22 Feb 2007 02:20:33 +0200 Ville Syrj__l__ wrote: > Replace a busy loop with mdelay() in atyfb clock setup code. This fixes > boot hangs several people have experienced. > > Signed-off-by: Ville Syrjala > --- > > This patch was already forwareded by James to some of you, but here it > is with the proper changelog, signed-off-by line, and a language fix in > the comment part. Also Cc:d stable@kernel.org as this seems like -stable > material to me. > > drivers/video/aty/mach64_ct.c | 9 +++------ > 1 file changed, 3 insertions(+), 6 deletions(-) > > Index: linux-2.6.20.1/drivers/video/aty/mach64_ct.c > =================================================================== > --- linux-2.6.20.1.orig/drivers/video/aty/mach64_ct.c > +++ linux-2.6.20.1/drivers/video/aty/mach64_ct.c > @@ -598,7 +598,6 @@ static void aty_resume_pll_ct(const stru > struct atyfb_par *par = info->par; > > if (par->mclk_per != par->xclk_per) { > - int i; > /* > * This disables the sclk, crashes the computer as reported: > * aty_st_pll_ct(SPLL_CNTL2, 3, info); > @@ -609,12 +608,10 @@ static void aty_resume_pll_ct(const stru > aty_st_pll_ct(SCLK_FB_DIV, pll->ct.sclk_fb_div, par); > aty_st_pll_ct(SPLL_CNTL2, pll->ct.spll_cntl2, par); > /* > - * The sclk has been started. However, I believe the first clock > - * ticks it generates are not very stable. Hope this primitive loop > - * helps for Rage Mobilities that sometimes crash when > - * we switch to sclk. (Daniel Mantione, 13-05-2003) > + * SCLK has been started. Wait for the PLL to lock. 5 ms > + * should be enough according to mach64 programmer's guide. > */ > - for (i=0;i<=0x1ffff;i++); > + mdelay(5); > } > > aty_st_pll_ct(PLL_REF_DIV, pll->ct.pll_ref_div, par); > A similar but different patch just got merged into mainline: commit 8690ba446defe2e2b81803756c099d2943dfd5fd Author: David Miller Date: Mon Mar 5 01:35:36 2007 -0800 [PATCH] video/aty/mach64_ct.c: fix bogus delay loop CT based mach64 cards were reported to hang on sparc64 boxes when compiled with gcc-4.1.x and later. Looking at this piece of code, it's no surprise. A critical delay was implemented as an empty for() loop, and gcc 4.0.x and previous did not optimize it away, so we did get a delay. But gcc-4.1.x and later can optimize it away, and we get crashes. Use a real udelay() to fix this. Fix verified on SunBlade100. Signed-off-by: David S. Miller Signed-off-by: Linus Torvalds diff --git a/drivers/video/aty/mach64_ct.c b/drivers/video/aty/mach64_ct.c index f3b487b..1fdcfdb 100644 --- a/drivers/video/aty/mach64_ct.c +++ b/drivers/video/aty/mach64_ct.c @@ -598,7 +598,6 @@ static void aty_resume_pll_ct(const stru struct atyfb_par *par = info->par; if (par->mclk_per != par->xclk_per) { - int i; /* * This disables the sclk, crashes the computer as reported: * aty_st_pll_ct(SPLL_CNTL2, 3, info); @@ -614,7 +613,7 @@ static void aty_resume_pll_ct(const stru * helps for Rage Mobilities that sometimes crash when * we switch to sclk. (Daniel Mantione, 13-05-2003) */ - for (i=0;i<=0x1ffff;i++); + udelay(500); } aty_st_pll_ct(PLL_REF_DIV, pll->ct.pll_ref_div, par); hopefully that works OK for you. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV