From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dirk Behme Date: Wed, 29 Apr 2009 18:48:36 +0200 Subject: [U-Boot] U-Boot Timer Qualification In-Reply-To: <20090428174726.C06BB83420E8@gemini.denx.de> References: <20090422204936.GB29252@game.jcrosoft.org> <200904271528.29873.vapier@gentoo.org> <20090428100806.GA4896@localhost.localdomain> <200904280848.14109.vapier@gentoo.org> <20090428151147.GA19683@linux-mips.org> <20090428174726.C06BB83420E8@gemini.denx.de> Message-ID: <49F884E4.3050709@googlemail.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Wolfgang Denk wrote: > Dear Ladislav Michl, > > In message <20090428151147.GA19683@linux-mips.org> you wrote: >> a lot of changes are entering arm tree, many without any commit message. >> And now we have some special cases which needs some special care for yet >> unclear reason. OMAP3 timer precission was discussed to death and patch >> still didn't went in, because it needs to be verified against some >> document you are claiming is not mandatory. > > Just in case there is any doubt here: > > There is no, and I say *no*, mandatory verification of any timing > precision in U-Boot. > > We all agree that precision is a good thing to have, it it must come > at a reasonable effort, and there is no reason to drive it into > extreme precision. To come back to the more practical part of this discussion ;) , my understanding of this is that we agree that http://lists.denx.de/pipermail/u-boot/2009-April/051204.html ( http://lists.denx.de/pipermail/u-boot/2009-April/051237.html ) should be applied? Best regards Dirk > Clock signals may need an accuracy of 1 or 2% or better - as we may > see character corruption if the baudrate generators are off too far - > but this is usually a hardware issue in the first place. > > System timers (like udelay() etc.) in U-Boot do not need such a level > of accuracy. That does not mean we should intentionally be inaccurate. > > And of course actual testing is good, and documentation of the test > results is even better. > > But: it is not mandatory. Not in U-Boot (and also not in Linux, to the > best of my knowledge). > >> I'll omit more comments to this topic until my objections get answered. >> Just one side note: Both methods can be easily set in code, freeing >> every and each developer from reimplementing test case. Such code could >> be one for all and selfexplaining. Is it worth doing using current timer >> API? > > See my previuous posting. I don;t think that a generic test method > that works on all boards would be possible. > > Best regards, > > Wolfgang Denk >