From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Cox Subject: Re: [PATCH 1/2] drm/kms: Make i2c buses faster Date: Fri, 21 Oct 2011 14:32:44 +0100 Message-ID: <20111021143244.4d1eac1e@lxorguk.ukuu.org.uk> References: <201110210908.30632.jdelvare@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from earthlight.etchedpixels.co.uk (earthlight.etchedpixels.co.uk [81.2.110.250]) by gabe.freedesktop.org (Postfix) with ESMTP id 6768F9E7DD for ; Fri, 21 Oct 2011 06:32:41 -0700 (PDT) In-Reply-To: <201110210908.30632.jdelvare@suse.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dri-devel-bounces+sf-dri-devel=m.gmane.org@lists.freedesktop.org Errors-To: dri-devel-bounces+sf-dri-devel=m.gmane.org@lists.freedesktop.org To: Jean Delvare Cc: dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org On Fri, 21 Oct 2011 09:08:30 +0200 Jean Delvare wrote: > A udelay value of 20 leads to an I2C bus running at only 25 kbps. A > value of 40 as the nouveau driver has is even slower at 12.5 kbps. I2C > devices can typically operate faster than this, 50 kbps should be fine > for all devices (and compliant devices can always stretch the clock is > needed.) That depends on your cable, drive and signal quality. It's not something you just turn up because it seems a good idea. Reliability is MUCH more important than shaving microseconds off monitor probe times. Alan