From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Mon, 29 Oct 2001 21:27:42 +0000 Subject: RE: [Linux-ia64] itc sync & clock_* Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Mon, 29 Oct 2001 15:35:02 -0500, "WEI,DONG (HP-Roseville,ex1)" said: Dong> Right now I need a description of the proposed flag to be Dong> included in the firmware architectural definition. The Dong> description should also include where (hardware register, or Dong> platform knowledge, etc.) firmware would get such information Dong> as to determine whether to set or clear the flag. As far as I'm concerned, there definitely needs to be a flag that indicates whether the ITCs are guaranteed to operate in lockstep (i.e., with zero drift among them). The flag would *not* indicate that the ITC are necessarily synchronized when the OS is started, just that if the OS synchronizes them, they'll be guaranteed to stay in lockstep. A secondary question is whether the flag should indicate whether the ITCs all run at the same frequency. At the moment, I don't believe this is a good idea, because frequency and drift are separate issues. Plus I *think* we should be able to handle the frequency question with PAL_FREQ_RATIOS and SAL_FREQ_BASE. But we need to verify this (the issue is whether measurement problems might cause PAL report slightly different frequencies for different ITCs, even when they're driven off the same clock and are therefore really the same). It would be good if someone else could take the lead on this because otherwise (and I'm sorry if I sound like a broken record) it will have to wait until the book is done (which will be another couple of weeks, really... ;-). --david