Mike, On Friday 01 February 2008, Mike Nuss wrote: > The following line in cpu/ppc4xx/start.S: > > mtspr tsr,r1 /* clear all timer exception status */ > > has the effect of clearing WRS, making it impossible for a watchdog device > driver (such as Linux's booke-wdt) to later check those bits to determine > whether a reset occurred. I assume the reason those bits are cleared by > U-Boot is because they are undefined on poweron reset. However, it's > possible to build a board with external logic to detect whether a poweron > reset occurred, as suggested by AMCC's application note on the watchdog > timer. > > We have built such a board. For now I have just commented out that line of > code, and later on in Linux I check the external logic, which requires > checking and setting GPIOs tied to a flip-flop. Obviously there is a better > solution. I think it would make sense to add a CFG option to U-Boot that > would have the following two effects: > > 1. Change that line so it clears all status except WRS > 2. In the board-specific code, once the GPIO controller has been > configured, check the flip flop there, and clear the bits if a poweron > reset occurred. Then Linux (or any OS) can simply look at those bits and > can depend on their contents being "as correct as possible" - on boards > without the external logic, it will simply always read 0, as it does now, > but on boards such as ours, it will reflect the actual status. > > Does this make sense? I can submit a patch.
Sure. Please go ahead. I'll probably comment in more details when you patch is available. Thanks. Best regards, Stefan ===================================================================== DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 Email: [EMAIL PROTECTED] ===================================================================== ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ U-Boot-Users mailing list U-Boot-Users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/u-boot-users
