From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Hogan Subject: Re: [PATCH 3/4] pinctrl: remove slew-rate parameter from tz1090 Date: Tue, 25 Jun 2013 15:57:08 +0100 Message-ID: <51C9AFC4.1020305@imgtec.com> References: <201306251455.01540.heiko@sntech.de> <201306251456.36499.heiko@sntech.de> <51C99581.2010403@imgtec.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Linus Walleij Cc: =?ISO-8859-1?Q?Heiko_St=FCbner?= , Stephen Warren , "linux-kernel@vger.kernel.org" , "devicetree-discuss@lists.ozlabs.org" , Grant Likely , Rob Herring List-Id: devicetree@vger.kernel.org On 25/06/13 14:22, Linus Walleij wrote: > Can't we just try to come up with a patch that nails down the meaning of > slew rate in some meaningful manner then? > > So according to: > http://en.wikipedia.org/wiki/Slew_rate > a proper expression for slew rate would be dV/dt i.e. > something like microvolts per microsecond (which then just > becomes volts/second). > > What we need to figure out is what range will be applicable within > reasonable doubt for current scenarios and the next few years. > > What are your datasheets specifying here, and what would be > a proper measure? My datasheet says: 0: slow (half frequency) 1: fast I just got a reply back from a hardware engineer, who said that the relationship with the actual volts/usec will depend on both the drive strength and the load on the pad, and that a definite answer probably requires running a simulation. Cheers James