Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 9 Mar 2001 02:53:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 9 Mar 2001 02:53:45 -0500 Received: from kerberos.suse.cz ([195.47.106.10]:33029 "EHLO kerberos.suse.cz") by vger.kernel.org with ESMTP id ; Fri, 9 Mar 2001 02:53:34 -0500 Date: Fri, 9 Mar 2001 08:53:03 +0100 From: Vojtech Pavlik To: Daniela Engert Cc: "linux-kernel@vger.kernel.org" Subject: Re: Linux 2.4.2ac12 (vt82c686 info) Message-ID: <20010309085303.A690@suse.cz> In-Reply-To: <20010308195107.A8509@suse.cz> <20010309072110.DB1C73E75@mail.medav.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <20010309072110.DB1C73E75@mail.medav.de>; from dani@ngrt.de on Fri, Mar 09, 2001 at 08:25:43AM +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 09, 2001 at 08:25:43AM +0100, Daniela Engert wrote: > >They're about the same - only Alan didn't like the PCI speed measurement > >code that's new in the 4.x series, so I added all the other changes to > >the 3.20 driver, and 3.21 was born. > > I do understand Alan's objections against this speed measurement code > very well. I have similar code built into other (non-Linux) drivers, > and according to the many user reports that I got the measurement > results should be taken with a grain of salt. It is working perfectly > in most cases, but it may fail from time to time. There is a hidden > assumption in this type of measurement which the device that you run > the test against has to fulfill. If it doesn't (and it is not required > to do to be conforming to the ATA spec), the measurement results (PCI > bus clock) are bogus (typically way too high). Actually I don't think my method can ever result in a measurement higher than real PCI clock, but can result in a lower one (if the device deasserts IORDY even on a speed slower than PIO_0), which is also a problem. Anyway, on fast machines the accuracy of the current algorithm is +- .01 MHz. Once tested a little more, the measurement will probably go in, however with an option for the user to override it with a command line parameter. Btw, if it isn't a secret - what other drivers are those and what is the exact method you used ... ? -- Vojtech Pavlik SuSE Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/