From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wproxy.gmail.com (wproxy.gmail.com [64.233.184.196]) by ozlabs.org (Postfix) with ESMTP id 9940467A64 for ; Fri, 8 Apr 2005 18:52:13 +1000 (EST) Received: by wproxy.gmail.com with SMTP id 57so674715wri for ; Fri, 08 Apr 2005 01:52:12 -0700 (PDT) Message-ID: <9b7ca65705040801455b84eb0d@mail.gmail.com> Date: Fri, 8 Apr 2005 17:45:22 +0900 From: Daniel Ann To: linuxppc-embedded Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Subject: Best way to determine tb_ticks_per_jiffy inside todc_calibrate_decr() Reply-To: Daniel Ann List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hey folks, I seem to have problem getting 1 second right. Board has no RTC so I've basically NULLed all the todc_XXX functions except todc_calibrate_decr. Now question is, what value should I be assigning it to tb_ticks_per_jiffy ? I was able to dig up some info from the archive, and it read, =-=-=-FROM ARCHIVE =-=-=- You must find this value by yourself but a good starting point is your frequency in Hz (I think) Example of the code unsigned int freq = 28000000; tb_tick_per_jiffy = freq/HZ; tb_to_us = mulhwu_scale_factor(freq,1000000); =-=-=-END OF ARCHIVE =-=-=- I'm fine with working it out myself but where do I start ? My board has 33MHz OSC, so I've trie freq = 33 * 1000000 (where HZ is defined 100) but it turned out to be little short. I could have just tried few more trial and error, but I prefer knowing what I'm doing so.. :) Before I was trying it with 100 * 1000000 which had delays like 10:1. Now its only about 1.5:1. So, I guess I'm on the right track.... so can anyone please help me out here? Also, could anyone spill their brain on mulhwu_scale_factor() ? I've followed the code and ended up reading what seems to be a assembler. (Should have paid attention during the lectures :P) Any hint on this ? Thanks heaps.. Cheers, -- Daniel